Dynamic anterior cervical plate system having moveable segments, instrumentation, and method for installation thereof

ABSTRACT

An anterior cervical plating system includes moveable plate segments to vary the overall length of the plate and allow and/or cause intersegmental compression of vertebral bodies. The plating system is capable of both passive and active dynamization and has the ability to produce the former from the latter.

RELATED APPLICATIONS

This application claims the benefit of provisional application No.60/379,589, filed May 9, 2002; and provisional application No.60/377,916, filed May 3, 2002; provisional application No. 60/356,318,filed Feb. 12, 2002; provisional application No. 60/355,194, filed Feb.8, 2002; provisional application No. 60/296,681, filed Jun. 6, 2001;provisional application No. 60/296,680, filed Jun. 6, 2001; provisionalapplication No. 60/296,060, filed Jun. 4, 2001; provisional applicationNo. 60/296,059, filed Jun. 4, 2001; all of which are incorporated byreference herein.

BACKGROUND

The use of plates, screws, and locks to prevent separation and backingout of screws from the plate, for use on the anterior aspect of thecervical spine to provide alignment and stability as an adjunct tofusion of adjacent vertebral bodies is known in the art. Also known inthe art is that compressive load, within a physiological range across afusion site, is beneficial to the fusion process. Conversely, a failureto maintain a compressive load across a fusion site, or to have a gap inthe fusion construct continuity may lead to a failure to achieve fusioncalled pseudoarthrosis. A primary purpose of the aforementioned cervicalhardware is to provide stability during the healing and fusion process.The fusion process occurs in part through a process called “creepingsubstitution” by which new living bone replaces the dead bone such asthat of a bone graft. The fusion process involves a phase of boneresorption as preliminary to the formation of the new bone. It ispossible then for the bone resorption to result in gaps in thecontinuity of the fusion mass, such that if the hardware is sufficientlyrigid, such as occurs as a result of increasing the strength of thecomponents and constraining the relationship of the screws to the plate,those gaps may persist and increase in size as the hardware holds thebone portions separated rather than allowing those bone portions to movetogether to close those gaps. This holding apart of the bone portions(called distraction) can therefore lead to a failure of fusion(pseudoarthrosis). These rigid systems by a combination of not inducingcompression at the fusion site and of holding the bone portions to befused apart may cause a “distraction pseudoarthrosis.”

Alternative cervical plating systems have attempted to preventdistraction pseudoarthrosis by allowing the vertebral bodies to collapsetowards each other as needed during the fusion process. Generally thishas been done by allowing the bone screws to be free to move relative tothe plate, that is, movement such as sliding, swiveling, rotating, andangulating, independent of whether the screws are prevented fromseparating or backing out of the plates such as by the use of locks.Undesired multidirectional instability can occur in such plating systemsthat is counter to the very purpose of such hardware which is toincrease or provide for stability.

Another approach to solving this problem has been to attach by screws ablock to each of the vertebral bodies to be fused and then to allowthose blocks to slide up and down on a pair of rods. Each of theseconstructs have in common that they sacrifice stability, the ability tohold the bones to be fused rigidly in place and prevent undesiredmotion; for the ability to allow, but not cause the vertebral bodies tocollapse.

There exists therefore a need for an improved anterior cervical platingsystem that is: (1) sufficiently rigid to maintain the desired alignmentof the vertebral bodies to be fused; (2) capable of inducing compressiveload across the fusion site; and/or (3) capable of allowing for themotion of the vertebral bodies towards each other to prevent or to closeany gaps in the continuity of the fusion construct, while still beingcapable of preventing motion in all other directions. When similarchallenges have been faced at other skeletal locations, the solutioninvolved anchoring the bone screws through the far cortex of the boneportions to be joined, in effect anchoring the screws in such a way asto make it possible for the screws to force movement of the plates. Inthe cervical spine anteriorly, however, it has been found to be highlyundesirable to drive the bone screws through the far cortex of thevertebral bodies, as this is where the spinal cord is located. Thereremains therefore a need for an improved cervical plating system as justdescribed that does not require that the bone screws penetrate the farcortex to achieve the desired purpose as described.

The size of the vertebral bodies and the spacing between the vertebralbodies varies from patient to patient. The height of the vertebralbodies and the discs therebetween may vary level by level even in thesame person. Thus, a plate of correct length does not necessarily havebone screw receiving holes correctly positioned to overlie the vertebralbodies in accordance with the spacing of the vertebral bodies to whichthe plate is to be applied. As a result, conventional plating systems ofthe past had to be manufactured in many different lengths and spacingconfigurations which were nevertheless fixed in an attempt to provideplates for many, though still possibly not all, of the various sizes andspacings of the vertebral bodies to which the plate was to be applied.For example, in a multi-segment plate the length of the plate would needto correspond to the overall length of the vertebral bodies to be joinedand actual distances therebetween and the screw holes of the platearranged to overlie the vertebral bodies. In order to cover the possiblerange of sizes, health care facilities would need to carry a largeinventory of different sizes of plates, in some cases as many as sixtydifferent sized plates would be needed. Such a large inventory is anexpensive undertaking and still worse, facilities with a high caseloadneed to invest in more than one of each plate size to provide for thepossibility of overlapping demand for the same plate size. Facilitieswith lower caseloads may find it prohibitively expensive to stock aninventory of plates sufficient to cover the range of possible sizes andthus might not be able to afford to stock a set at all or have less thanall sizes of plates needed for all cases. Manufactures cannot afford toplace a set of plates on consignment in facilities with low caseloads asthe number of sales would not cover the carrying costs of the plates.

There exists therefore a need for an improved anterior cervical platingsystem that (1) allows for the overall adjustability of the length ofthe plate; (2) allows for variations in spacing between the bone screwreceiving holes of the plate portions corresponding to the attachmentpoint of the plate to the vertebral bodies; (3) reduces the requisiteplate inventory; and (4) can avoid or prevent distractionpseudoarthrosis without itself introducing multidirectional instability.

SUMMARY OF THE INVENTION

The present invention in one preferred embodiment is a dynamic anteriorcervical plating system including a plate comprising segments inmoveable relationship to each other adapted to allow for the overalladjustability of the length of the plate and for variations in theintersegmental spacing of the bone screw receiving holes, to createand/or store a compressive load across a disc space between two adjacentvertebral bodies to be fused, and/or to allow motion of the vertebralbodies toward each other to prevent or close gaps in the continuity of afusion construct, while preferably preventing motion in all otherdirections when in use. As used herein, a spinal fusion segment isdefined as two vertebral bodies with an intervertebral implant, made ofbone or an artificial material, in the disc space therebetween. As usedherein, a fusion construct is defined as a spinal fusion segment plusthe hardware, such as a plate and screws for example.

The present invention in another preferred embodiment is a dynamic,modular, anterior cervical plating system including a plate comprisingassembleable segments in moveable relationship to each other adapted toallow for the overall adjustability of the length of the plate and forvariations in the intersegmental spacing of the bone screw receivingholes, to create and/or store a compressive load across a disc spacebetween two adjacent vertebral bodies to be fused, and/or to allowmotion of the vertebral bodies toward each other to prevent or closegaps in the continuity of a fusion construct, while preferablypreventing motion in all other directions when in use.

The ability to permit the movement of adjacent vertebral bodies towardone another is referred to herein as “dynamization.” Dynamization may be“passive” allowing the plate to shorten when a shortening force, such asa compressive load is applied. Dynamization may be “active” wherein theplating system stores energy to induce shortening of the fusionconstruct should the opportunity present. The present invention platingsystem may passively dynamize, actively dynamize, provide a combinationof both, as well as convert and store certain compressive stressesencountered during the healing phase as will be more fully describedherein.

The plate segments also can be moved to vary the spacing between theplate segments as well as the overall length of the plate so that thesize of the plate may be adjusted to correspond to a range of sizes andspacing of the adjacent vertebral bodies to which the plate is beingapplied; thereby greatly reducing the inventory of plate sizes needed.The moveable plate segments combine to form the plate. Each platesegment is attached to a vertebral body to be fused by at least one bonescrew and preferably a pair of bone screws, which when inserted, arepreferably prevented from backing out of the plate by at least onelocking element adapted to lock at least two bone screws to the plate.In an alternative embodiment, a locking element is adapted to lock asingle bone screw to the plate.

The paths of the bone screws through the plate may be fixed or variable.If the paths are variable, they may be more or less stable depending onhow resistant to motion the screws are relative to the plate when thescrews are locked to the plate. To the extent that screws aresufficiently stable in relation to the plate to make use of the presentinventive teaching, these screw, plate, and lock combinations orvariations thereon are also within the broad scope of the presentinvention.

In a preferred embodiment of the present invention, after each of thesegments of the plate are attached to a respective one of the vertebralbodies to be fused, the plate is capable of movement from a first orelongated position to a second or shorter position, a process generallyreferred to as “passive dynamization”—that is the ability of the systemto allow the plated spinal segment to shorten in response to unmetcompressive loads to allow for the bone portions to be fused to moveclose together to restore contact. A preferred embodiment of thispresent invention is capable of allowing for this passive dynamizationwhile preventing undesirable motions along and around all axes otherthan the motion along the longitudinal axis of the plate.

In another preferred embodiment of the present invention, the platesegments are articulated in such a way that even the one freedom ofmovement that is along the longitudinal axis of the plate is selectivelylimited to the desired passive dynamization that is shortening of theplate construct. This preferred embodiment of the present invention willshorten as required to maintain loaded contact of the bone portions tobe fused, and if challenged, resist any forces such as those that wouldaccompany cervical extension that would distract or destabilize theconstruct by elongating it. A further benefit of this embodiment is itsability to store and impart a compressive load across the fusion sitereferred to herein as “active dynamization” wherein energy stored in thesystem shortens the plate construct if conditions permit. This load canbe applied by the surgeon at the time of surgery and/or be producedduring the healing phase by harnessing the compressive loads such asoccur randomly with neck motion. Compressive load within a physiologicalrange has been shown to have a beneficial effect on the healing of bone.The induction of a compressive load across vertebral bodies to be fused,induces bone growth and when bone resorption occurs at the interface ofthe graft or implant and the vertebral bodies to be joined, thosevertebral bodies are urged to move closer together, thus avoiding theformation of a gap therebetween and thereby acting to mitigate againstpseudoarthrosis.

Alternatively, various embodiments of the present invention allow thesurgeon to induce a desired amount of preload (compressive force) acrossthe fusion site and to permit a desired amount of shortening of theconstruct—“active dynamization” should the opportunity occur; and yetlock the system to prevent any further shortening as might present arisk of deformity or be otherwise undesirable. Such a system urges thebone portions closer together.

In a preferred embodiment, a pre-load force can be applied to the platesegments such that while the plate segments may undergo no added motioninitially, there is a selective force applied to the plate segments andthe plate segments are capable of motion in only one direction, suchthat should resorption occur at one of the fusion interfaces then theplate segments are not only free to move in a direction toward oneanother, and only in that direction, but are also urged to do so torelieve that preload force. Such a system urges the vertebral bodiestogether over time as resorption permits.

Alternatively, in another embodiment of the plate of the presentinvention, a desired amount of preload (compressive force) may beinduced across the fusion site to permit active dynamization should theopportunity occur, without locking the system such that after activedynamization is exhausted (if exhausted), then the plate will stillallow passive dynamization to occur thereafter.

In another embodiment of the present invention, the plate includes astructural feature such as a groove, recess, slot, cam, or pivot, withinits physical perimeter to engage a tool to cooperatively move segmentsof the plate towards each other. These embodiments of the presentinvention may be adapted to allow for passive, active, or active pluspassive dynamization, and when used to store compressive load to allowfor or prevent further motion thereafter. In a preferred version of thisembodiment, the structural feature contained within the plate forgenerating the compressive load and/or shortening the plate, may alsoserve as the locking mechanism to limit the amount of further shorteningpossible.

Various embodiments of the plating system of the present inventionprovide one or more of the following advantages:

1. The requisite plate inventory is reduced as each plate may cover arange of sizes. The plate of the present invention includes multiplesegments which may be of varying sizes wherein the segments are adaptedto be assembled so as to be adjustable to provide for the size andspacing apart of the vertebral bodies to which the plate is to beapplied. The plate may have its segments moved relative to one anotherso that the spacing between the plate segments may be adjusted so as tocorrespond to the actual distances between the vertebral bodies to befused in a multi-segment construct for a more precise fit. The height ofthe discs and the vertebral bodies may vary level by level even in thesame person. Thus, the ability to adjust the distances between thesegments of the plates that correspond to the attachments to thosevertebral bodies allows for a more precise fit of the plate to the spinewith a reduced inventory of the number of plates required to do so.

2. It is possible to precisely contour each segment separately.

3. The plating system of the present invention reduces the risk that theplate construct will be discovered to be too short or too long after theattachment process has commenced.

4. It is possible to compress and dynamize levels selectively.

5. The fasteners that link the segments can be tightened to lock thesegments after they are compressed or, alternatively, can allow forfurther motion of the plate segments together.

6. The same hardware can provide for passive dynamization or be rigidlyfixed depending on the fasteners used to link plate segments.

7. The system can allow for passive dynamization, active dynamization,the combination of passive and active dynamization, or can convert bodymotion into active dynamization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exploded top perspective view of a plate, a fastener, anda locking element in accordance with a preferred embodiment of thepresent invention.

FIG. 1B is an exploded top perspective view of a plate, a fastener, anda locking element in accordance with another preferred embodiment of thepresent invention.

FIG. 1C is an exploded top perspective view of a plate, a fastener, andlocking elements in accordance with another preferred embodiment of thepresent invention.

FIG. 1D is an exploded top perspective view of a plate, a fastener, andlocking elements in accordance with another preferred embodiment of thepresent invention.

FIG. 2A is an exploded bottom perspective view of the plate, fastener,and locking element of FIG. 1A.

FIG. 2B is an exploded bottom perspective view of the plate, fastener,and locking element of FIG. 1B.

FIG. 2C is an exploded bottom perspective view of the plate, fastener,and locking elements of FIG. 1C.

FIG. 2D is an exploded bottom perspective view of the plate, fastener,and locking elements of FIG. 1D.

FIG. 3A is a top plan view of the plate, fastener, and locking elementof FIGS. 1A and 1B.

FIG. 3C is a top plan view of the plate, fastener, and locking elementsof FIGS. 1C and 1D.

FIG. 4A is a bottom plan view of the plate, fastener, and lockingelement of FIG. 1A.

FIG. 4B is a bottom plan view of the plate, fastener, and lockingelement of FIG. 1B.

FIG. 4C is a bottom plan view of the plate, fastener, and lockingelements of FIG. 1C.

FIG. 4D is a bottom plan view of the plate, fastener, and lockingelements of FIG. 1D.

FIG. 5A is an end view of the plates of FIGS. 1A–1D.

FIG. 6A is a side elevation view of the plates of FIGS. 1A and 1B.

FIG. 6C is a side elevation view of the plates of FIGS. 1C and 1D.

FIG. 7A is a partial cross sectional view of the plates of FIGS. 1A and1C.

FIG. 7B is a partial cross sectional view of the plates of FIGS. 1B and1D.

FIG. 8A is an enlarged fragmentary view of the plates of FIGS. 1A and 1Cand an alternative embodiment of a fastener in accordance with thepresent invention.

FIG. 8B is an enlarged fragmentary view of the plates of FIGS. 1B and 1Dand an alternative embodiment of a fastener in accordance with thepresent invention.

FIG. 9A is an enlarged fragmentary cross sectional view of an embodimentof the ratchetings in the upper and lower portions of the plates ofFIGS. 1A–1D in a first position.

FIG. 10A is a fragmentary cross sectional view of FIG. 9A in a secondposition.

FIG. 11A is an enlarged fragmentary cross sectional view of a preferredembodiment of the ratchetings in the upper and lower portions of theplates of the present invention in a first position.

FIG. 12A is a fragmentary cross sectional view of FIG. 11A in a secondposition.

FIG. 13A is a top perspective view of the plates and fasteners of FIGS.1A and 1B and instrumentation for compressing the plates andinstrumentation for locking the fasteners in accordance with a preferredembodiment of the present invention.

FIG. 13C is a top perspective view of the plates and fasteners of FIGS.1C and 1D and instrumentation for compressing the plates andinstrumentation for locking the fasteners in accordance with a preferredembodiment of the present invention.

FIG. 14A is a top plan view of the plates and fasteners of FIGS. 1A and1B in a compressed state with the instrumentation of FIG. 13A shown incross section engaging the ends of the plate to compress the plate inthe direction of the arrows and with the instrumentation engaging thefastener.

FIG. 14C is a top plan view of the plates and fasteners of FIGS. 1C and1D in a compressed state with the instrumentation of FIG. 13C shown incross section engaging the ends of the plate to compress the plate inthe direction of the arrows and with the instrumentation engaging thefastener.

FIG. 15A is a partial cross sectional view along line 15A—15A of FIG.14A for the plate of FIG. 1A.

FIG. 15B is a partial cross sectional view along line 15A—15A of FIG.14A for the plate of FIG. 1B.

FIG. 15C is a partial cross sectional view along line 15C—15C of FIG.14C for the plate of FIG. 1C.

FIG. 15D is a partial cross sectional view along line 15C—15C of FIG.14C for the plate of FIG. 1D.

FIG. 16A is a top perspective view of a plate, a fastener, and lockingelement in accordance with another preferred embodiment of the presentinvention.

FIG. 16C is a top perspective view of a plate, a fastener, and lockingelements in accordance with another preferred embodiment of the presentinvention.

FIG. 17A is a top plan view of the plate and fastener of FIG. 16A.

FIG. 17C is a top plan view of the plate, fastener, and locking elementsof FIG. 16C.

FIG. 18A is a top plan view of the plate of FIG. 16A in an elongatedstate with fastener.

FIG. 18C is a top plan view of the plate of FIG. 16C in an elongatedstate, fastener, and locking elements.

FIG. 19A is a bottom plan view of the plate and fastener of FIG. 16A.

FIG. 19B is a bottom plan view of another preferred embodiment of theplate and fastener of FIG. 16A.

FIG. 19C is a bottom plan view of the plate and fastener of FIG. 16C.

FIG. 19D is a bottom plan view of another preferred embodiment of theplate and fastener of FIG. 16C.

FIG. 20A is a partial cross sectional view along line 20A—20A of theplate of FIG. 17A.

FIG. 20B is a partial cross sectional view along line 20A—20A of FIG.17A of a plate and fastener in accordance with another preferredembodiment of the present invention.

FIG. 21A is an exploded top perspective view of the plate, fastener, andlocking element of FIG. 16A.

FIG. 21B is an exploded top perspective view of the plate, fastener, andlocking element of FIG. 16A in accordance with another preferredembodiment of the present invention.

FIG. 21C is an exploded top perspective view of the plate, fastener, andlocking elements of FIG. 16C.

FIG. 21D is an exploded top perspective view of the plate, fastener, andlocking elements of FIG. 16C in accordance with another preferredembodiment of the present invention.

FIG. 22A is an exploded bottom perspective view of the plate, fastener,and locking element of FIG. 16A.

FIG. 22B is an exploded bottom perspective view of the plate, fastener,and locking element of FIG. 21B.

FIG. 22C is an exploded bottom perspective view of the plate, fastener,and locking elements of FIG. 16C.

FIG. 22D is an exploded bottom perspective view of the plate, fastener,and locking elements of FIG. 21D.

FIG. 23A is a top plan view of the plate and fastener of FIG. 16A and apartial fragmentary perspective view of an instrument for compressingthe plate and securing the fastener in accordance with another preferredembodiment of the present invention.

FIG. 23C is a top plan view of the plate, fastener, and locking elementsof FIG. 16C and a partial fragmentary perspective view of an instrumentfor compressing the plate and securing the fastener in accordance withanother preferred embodiment of the present invention.

FIG. 24A is an enlarged cross sectional view of the plate of FIG. 16Awith the instrument of FIG. 23A engaging the fastener and positionedwithin the plate.

FIG. 24B is an enlarged cross sectional view of another preferredembodiment of the plate of FIG. 16A with the instrument of FIG. 23Aengaging the fastener and positioned within the plate.

FIG. 24C is an enlarged cross sectional view of the plate of FIG. 16Cwith the instrument of FIG. 23C engaging the fastener and positionedwithin the plate.

FIG. 24D is an enlarged cross sectional view of another preferredembodiment of the plate of FIG. 16C with the instrument of FIG. 23Cengaging the fastener and positioned within the plate.

FIG. 25A is a fragmentary top plan view of one of the plates of FIGS.16A and 16C in an elongated state with the instrument of FIGS. 23A and23C shown in cross section engaging the fastener and positioned withinthe plate.

FIG. 26A is a fragmentary top plan view of one of the plates of FIGS.16A and 16C in a compressed state with the instrument of FIGS. 23A and23C shown in cross section engaging the fastener and positioned withinthe plate to rotate the fastener in the direction of the arrow tocompress the plate.

FIG. 27A is an exploded top perspective view of a plate, a fastener, andlocking element in accordance with another preferred embodiment of thepresent invention.

FIG. 27B is an exploded top perspective view of a plate, a fastener, andlocking element in accordance with another preferred embodiment of thepresent invention.

FIG. 27C is an exploded top perspective view of a plate, a fastener, andlocking elements in accordance with another preferred embodiment of thepresent invention.

FIG. 27D is an exploded top perspective view of a plate, a fastener, andlocking elements in accordance with another preferred embodiment of thepresent invention.

FIG. 28A is a cross sectional view transverse to the longitudinal axisof the plate of FIGS. 27A–27D.

FIG. 29A is a top plan view of a plate, fasteners, and locking elementin accordance with another preferred embodiment of the presentinvention.

FIG. 29C is a top plan view of a plate, fasteners, and locking elementsin accordance with another preferred embodiment of the presentinvention.

FIG. 30A is an exploded top perspective view of the plate, fasteners,and locking element of FIG. 29A.

FIG. 30B is an exploded top perspective view of another preferredembodiment of the plate, fasteners, and locking element of FIG. 29A.

FIG. 30C is an exploded top perspective view of the plate, fasteners,and locking elements of FIG. 29C.

FIG. 30D is an exploded top perspective view of another preferredembodiment of the plate, fasteners, and locking elements of FIG. 29C.

FIG. 31A is an exploded bottom perspective view of the plate, fasteners,and locking element of FIG. 30A.

FIG. 31B is an exploded bottom perspective view of the plate, fasteners,and locking element of FIG. 30B.

FIG. 31C is an exploded bottom perspective view of the plate, fasteners,and locking elements of FIG. 30C.

FIG. 31D is an exploded bottom perspective view of the plate, fasteners,and locking elements of FIG. 30D.

FIG. 32A is a top plan view of the plates, fasteners, and lockingelement of FIGS. 30A and 30B.

FIG. 32C is a top plan view of the plates, fasteners, and lockingelements of FIGS. 30C and 30D.

FIG. 33A is a bottom plan view of the plate and fasteners of FIG. 30A.

FIG. 33B is a bottom plan view of the plate and fasteners of FIG. 30B.

FIG. 33C is a bottom plan view of the plate, fasteners, and lockingelements of FIG. 30C.

FIG. 33D is a bottom plan view of the plate, fasteners, and lockingelements of FIG. 30D.

FIG. 34A is a side elevation view of the plates of FIGS. 30A and 30B.

FIG. 34C is a side elevation view of the plates of FIGS. 30C and 30D.

FIG. 35A is a partial cross sectional view along the longitudinal axisof the plate of FIG. 30A.

FIG. 35B is a partial cross sectional view along the longitudinal axisof the plate of FIG. 30B.

FIG. 35C is a partial cross sectional view along the longitudinal axisof the plate of FIG. 30C.

FIG. 35D is a partial cross sectional view along the longitudinal axisof the plate of FIG. 30D.

FIG. 36A is a top plan view of the plates in an elongated position,fasteners, and locking element of FIGS. 30A and 30B.

FIG. 36C is a top plan view of the plates in an elongated position,fasteners, and locking elements of FIGS. 30C and 30D. FIG. 37A is a topperspective view of one of the plates of FIGS. 30A and 30B and anotherpreferred embodiment of instrumentation for compressing the plate andinstrumentation for locking the fastener in accordance with the presentinvention.

FIG. 37C is a top perspective view of one of the plates of FIGS. 30C and30D and another preferred embodiment of instrumentation for compressingthe plate and instrumentation for locking the fastener in accordancewith the present invention.

FIG. 38A is a top plan view of one of the plates of FIGS. 30A and 30B ina compressed state with the instrumentation of FIG. 37A shown in crosssection engaging the ends of the plate to compress the plate in thedirection of the arrows, an alternative embodiment of instrumentationfor engaging an intermediary portion of the plate to compress the platein the direction of the arrows in dotted line, and instrumentationengaging the fastener and positioned within the plate.

FIG. 38C is a top plan view of one of the plates of FIGS. 30C and 30D ina compressed state with the instrumentation of FIG. 37C shown in crosssection engaging the ends of the plate to compress the plate in thedirection of the arrows, an alternative embodiment of instrumentationfor engaging an intermediary portion of the plate to compress the platein the direction of the arrows in dotted line, and instrumentationengaging the fastener and positioned within the plate.

FIG. 39A is a side elevation view of the plate of FIG. 38A with theinstrumentation shown in partial fragmentary, hidden line, and crosssectional views.

FIG. 39C is a side elevation view of the plate of FIG. 38C with theinstrumentation shown in partial fragmentary, hidden line, and crosssectional views.

FIG. 40A is an exploded top perspective view of a plate, fasteners, anda locking element in accordance with another preferred embodiment of thepresent invention.

FIG. 40B is an exploded top perspective view of a plate, fasteners, anda locking element in accordance with another preferred embodiment of thepresent invention.

FIG. 40C is an exploded top perspective view of a plate, fasteners, andlocking elements in accordance with another preferred embodiment of thepresent invention.

FIG. 40D is an exploded top perspective view of a plate, fasteners, andlocking elements in accordance with another preferred embodiment of thepresent invention.

FIG. 41 is a top plan view of a plate, fasteners, and locking elementsin accordance with another preferred embodiment of the presentinvention.

FIG. 42 is an exploded top plan view of a plate, fasteners, and lockingelements in accordance with another preferred embodiment of the presentinvention.

FIG. 43 is an enlarged fragmentary cross sectional view of the plate,locking element, and bone screws of FIG. 42.

FIG. 44 is an enlarged fragmentary cross sectional view of a plate,locking element, and bone screws in accordance with another embodimentof the present invention.

FIG. 45 is a fragmentary top plan view of another preferred embodimentof a plate and a locking element adapted to lock at least two bonescrews and a fastener in accordance with the present invention.

FIG. 46 is a fragmentary top plan view of another preferred embodimentof a plate and a locking element adapted to lock at least two bonescrews and a fastener in accordance with the present invention.

FIG. 47 a is an enlarged fragmentary cross sectional view of a lockingelement and bone screw in accordance with a preferred embodiment of thepresent invention.

FIG. 47 b is an enlarged fragmentary cross sectional view of a lockingelement and bone screw in accordance with another preferred embodimentof the present invention.

FIG. 47 c is an enlarged fragmentary cross sectional view of a lockingelement and bone screw in accordance with yet another embodiment of thepresent invention.

FIG. 47 d is an enlarged fragmentary cross sectional view of the lockingelement and bone screw of FIG. 47 c in an angled position.

FIG. 47 e is an enlarged fragmentary cross sectional view of aself-locking bone screw in accordance with a further embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference will now be made in detail to the present preferredembodiments (exemplary embodiments) of the invention, examples of whichare illustrated in the accompanying drawings. Wherever possible, thesame reference numbers will be used throughout the drawings to refer tothe same or like parts.

The present invention is for use in the cervical spine wheredynamization is highly desired to prevent distraction pseudoarthrosisand to maintain a compressive load across the fusion interfaces. Thepresent invention in one preferred embodiment is directed to a cervicalplate generally having at least two movable segments that are attachedto the vertebral bodies to be fused and connected in such a way as topermit dynamization of the vertebral bodies preferably along thelongitudinal axis of the plate. The movement of the segments relative toone another may be accompanied by a reduction in the overall length ofthe plate.

Where possible, the reference numerals in the figures are followed by aletter “a”, “b”, “c”, or “d” corresponding to preferred embodiments ofthe present invention, respectively. For example, a description of afeature identified by a reference numeral followed by the referenceletter “a” and also applicable to a feature identified by a referencenumeral followed by a letter “b”, “c”, or “d” will not be repeated foreach of the corresponding reference numerals.

FIGS. 1A, 2A, 3A, 4A, 5A, 6A and 7A show a preferred embodiment of acervical plate 100 a in accordance with the present invention. Plate 100a is preferably formed of a first segment 102 a and a second segment 104a in moveable relationship to one another. First and second segments 102a, 104 a can be of various lengths and/or configurations such that whenthe segments are assembled preferably overlapping at least in part,plates of various lengths and/or configurations can be formed to cover arange of sizes. First and second segments 102 a, 104 a can be of thesame or different lengths and can be coupled to each other or to anintermediate segment as shown in FIGS. 29A, 30A, 31A, 32A, 33A, 34A,35A, 36A, 37A, 38A, 39A, and -40A and described below in connection withother preferred embodiments of the present invention. The overall lengthof plate 100 a and the spacing of segments 102 a, 104 a can be adjustedby moving segments 102 a, 104 a relative to one another.

In this preferred embodiment of the present invention, a detachablefastener 106 a couples together first and second segments 102 a, 104 a.Fastener 106 a is configured to be detachably attached to at least oneof first and second segments 102 a, 104 a, to permit the assembly of twoor more plate segments. Fastener 106 a is detachable to permit for theassembly of the plate segments by the surgeon and allows for thecomplete uncoupling of first and second segments 102 a, 104 a from oneanother. As used herein, “detachable fastener” is defined as a fastenerthat can be assembled by the surgeon at the time of use and onceattached is meant to still be removable and then reattachable by thesurgeon. As shown in FIG. 7A, fastener 106 a, for example, may beembodied in the form of a screw having a head 108 a, a shaft 112 a, anda thread 116 a.

As shown in FIG. 8A, in another preferred embodiment fastener 106 a′ maybe configured to be tightened to only one of first and second platesegments 102 a, 104 a so as to permit movement of first and secondsegments 102 a, 104 a relative to one another when fastener 106 a′ isfully tightened. For example, fastener 106 a′ may have a shoulder 110 aadapted to bear upon second segment 104 a as indicated by arrow C.Shoulder 110 a is dimensioned so as to create a gap 111 a between head108 a′ and first segment 102 a so as to still permit a specific anddesired motion of first and second segments 102 a, 104 a relative to oneanother when fastener 106 a′ is fully tightened. The limited motion offirst and second segments 102 a, 104 a relative to one another providesfor dynamization of the spinal segment to be fused in that thosevertebral bodies are allowed to move closer together to maintaincontact.

As shown in FIGS. 1A and 2A, first segment 102 a preferably has an uppersurface 118 a, a lower surface 120 a, a medial portion 122 a, and an end124 a. First segment 102 a preferably includes bone screw receivingholes 126 a proximate end 124 a. Bone screw receiving hole 126 a ispreferably configured to receive a single bone screw or the bone screwreceiving holes also may be configured to receive more than one bonescrew. By way of example only and not limitation, a bone screw receivinghole may be in the form of a slot sized to receive at least two bonescrews.

Preferably, at least two of bone screw receiving holes 126 a may beoriented in plate 100 a to overlie the anterior aspect of a singlecervical vertebral body adjacent a disc space to be fused, though theinvention is not so limited. For example, a first pair of bone screwreceiving holes 126 a may be configured to overlie the anterior aspectof a first cervical vertebral body adjacent a disc space to be fused andat least a second pair of bone screw receiving holes 126 a may beoriented in plate 100 a to overlie the anterior aspect of a secondcervical vertebral body adjacent the disc space to be fused.

Bone screw receiving hole 126 a may, though need not be, configured toform an interference fit with at least a portion of the trailing end ofa properly dimensioned bone screw to be received therein. Bone screwreceiving holes 126 a may be configured, for example only, so that atleast one of bone screw receiving holes 126 a may hold a bone screw in afixed relationship to the plate or may hold a bone screw in a moveablerelationship, such as a variable angular relationship, described below.By way of example only and not limitation, bone screw receiving hole 126a may have a reduced dimension proximate lower surface 120 a of segment102 a to form a seat 127 a. Seat 127 a may have a surface adapted tocontact at least a portion of a bone screw inserted therein. The surfacemay be at least in part planar, at least in part curved, or have anyother configuration suitable for contacting at least a portion of a bonescrew.

End 124 a of first segment 102 a may also include a tool engagement area128 a adapted to cooperatively engage instrumentation for holding plate100 a and instrumentation for moving first and second segments relativeto one another to induce a desired amount of compressive force acrossthe fusion sites and to permit a desired amount of shortening of plate100 a. Medial portion 122 a preferably has a fastener receiving opening130 a adapted to accommodate fastener 106 a to couple first and secondsegments 102 a, 104 a to one another.

Fastener receiving opening 130 a is preferably configured to permitselected movement of fastener 106 a therein and to permit selectedmotion of first and second segments 102 a, 104 a along the longitudinalaxis of plate 100 a. Fastener receiving opening 130 a may include ashoulder 132 a recessed from upper surface 118 a of first segment 102 aadapted to contact the underside of head 108 a of fastener 106 a in thetightened position to prevent movement of first and second segments 102a, 104 a relative to one another. Alternatively, if a fastener 106 a′ isused, shoulder 110 a contacts second segment 104 a and the underside ofhead 108 a′ is positioned relative to shoulder 132 a to permit movementof first and second segments 102 a, 104 a relative to each other alongthe longitudinal axis of the plate when in the tightened positionproviding for dynamization of the vertebral bodies to be fused to occur,if needed. Fastener 106 a and fastener receiving opening 130 a cooperateto prevent complete uncoupling of first and second segments 102 a, 104 afrom one another when fastener 106 a is installed. For example, fastenerreceiving opening 130 a may be configured to prevent head 108 a offastener 106 a from passing therethrough.

Lower surface 120 a of first segment 102 a includes a tab receivingrecess 134 a for receiving a tab 136 a described below.

Second segment 104 a has an upper surface 138 a, a lower surface 140 a,a medial portion 142 a, and an end 144 a. Second segment 104 apreferably has bone screw receiving holes 126 a proximate end 144 a. End144 a may also include a tool engagement area 146 a adapted tocooperatively engage instrumentation for holding plate 100 a andinstrumentation for moving first and second segments 102 a, 104 arelative to one another to induce a desired amount of compressive forceacross the fusion site and to permit a desired amount of shortening ofplate 100 a. Medial portion 142 a preferably includes a fastenerreceiving opening 148 a for receiving a portion of fastener 106 a. Asfirst and second segments of plate 100 a are modular and assembleable,fastener receiving opening 148 a is configured to permit detachableattachment of fastener 106 a.

Fastener receiving opening 148 a preferably has a thread 150 a adaptedto engage with thread 116 a of fastener 106 a. The threaded engagementof fastener 106 a to fastener receiving opening 148 a permits firstsegment 102 a and second segment 104 a to be attached to each other whenfastener 106 a is sufficiently rotated and tightened. As fastener 106 ais rotated further, first and second segments 102 a, 104 a are securedtogether and locked and do not move relative to each other.Alternatively, if fastener 106 a′ shown in FIG. 8A is used in thetightened position, first and second segments 102 a, 104 a are capableof moving relative to each other.

Lower surfaces 120 a, 140 a of first and second segments 102 a, 104 aare preferably at least in part concave along at least a portion of thelongitudinal axis of the plate, may be biconcave at least in part, thatis, concave along the longitudinal axis of plate 100 a and concavetransverse to the longitudinal axis of the plate, or may have any shapesuitable for the intended purpose transverse to the longitudinal axis ofthe plate. A person skilled in the art will appreciate that plate 100 amay be adapted for other curvatures or have no curvature withoutdeparting from the intended purpose within the broad scope of thepresent invention. Lower surfaces 120 a, 140 a are preferably adapted tocontact at least a portion of the vertebral bodies to be fused and maybe configured to conform to the anterior aspect of at least a portion ofthe vertebral bodies.

Second segment 104 a preferably includes a tab 136 a extending frommedial portion 142 a. Tab 136 a is configured to cooperatively engage atab receiving recess 134 a in the lower surface 120 a of first segment102 a. Tab 136 a acts as a spring to maintain first and second segments102 a, 104 a aligned along the longitudinal axis of plate 100 a. Tab 136a also functions to limit movement of first segment 102 a in a directiontransverse to longitudinal axis of plate 100 a to prevent end 124 a fromdropping down beyond a desired position. This limited movement of firstsegment 100 a prevents medial portion 122 a of first segment 102 a fromlifting away from medial portion 142 a beyond a desired position, sothat ratchetings 150 a are not overly separated and rendered lesseffective as described in more detail below. It is appreciated thatother configurations of segments 102 a, 104 a are possible to hold apartsegments 102 a, 104 a and to limit movement of the segments in adirection transverse to the longitudinal axis of the plate. For example,the longitudinal curvatures of first and second segments 102 a, 104 acan be slightly different to spring apart segments 102 a, 104 a. Forexample, the radius of curvature of the lower surface of segment 102 amay be different than the radius of curvature of the upper surface ofsegment 104 a.

At least a portion of lower surface 120 a of first segment 102 a andupper surface 138 a of second segment 104 a are preferably configured tointerdigitate with one another to permit selected adjustment of thelength of plate 100 a. For example, lower surface 120 a and uppersurface 138 a may include a surface configuration, such as ratchetings152 a, configured to cooperatively interdigitate to permit selected andsequential movement along the longitudinal axis of plate 100 a. Theratchetings are preferably biased to allow movement in one preferreddirection along the longitudinal axis of the plate so as to allowshortening of the plate and resist lengthening of the plate.

FIGS. 9A and 10A show an embodiment of ratchetings having aconfiguration that is useful if no movement of first and second segments102 a, 104 a is desired after fastener 106 a is tightened. A preferredangular relationship of the cross section of ratchetings 152 a ₁ is a45-45-90 degree triangular relationship. As shown in FIG. 9A, in a firstposition, the peaks and valleys of ratchetings 152 a ₁ are cooperativelymating. Ratchetings 152 a ₁ permit for the fixed positioning of firstand second segments 102 a, 104 a relative to one another to create aselected length of plate 100 a. As shown in FIG. 10A, the peaks andvalleys are separated to permit movement of the first and secondsegments in the directions of the arrows along the longitudinal axis ofplate 100 a. In order for first and second segments 102 a, 104 a to moverelative to one another, there must be sufficient freedom of movementfor the segments to move apart in order to clear the height of the peaksof ratchetings 152 a ₁. Accordingly, in a preferred embodiment fastener106 a is configured to have at least one position that permits movementof the first and second segments along the longitudinal axis of plate100 a as well as along an axis transverse to the longitudinal axis ofplate 100 a such that ratchetings 152 a can move apart. Fastener 106 acan be tightened to a second position to resist or prevent movement ofsegments 102 a, 104 a relative to one another. For example, movement ofsegments 102 a, 104 a can be resisted in a direction along at least aportion of the longitudinal axis of plate 100 a.

FIGS. 11A and 12A show another preferred embodiment of ratchetings 152 a₂ having a forward-facing configuration for permitting movement in asingle direction. The configuration of ratchetings 152 a ₂ is usefulwhen movement of first and second segments 102 a, 104 a is desired topermit further shortening of the plate. A preferred angular relationshipof the triangular cross section of ratchetings 152 a ₂ is a 30-60-90degree triangular relationship. As shown in FIG. 12A, due to the forwardfacing angle of ratchetings 152 a ₂, sliding movement of first andsecond segments 102 a, 104 a in the direction, as indicated by thearrow, along the longitudinal axis of plate 100 a is facilitated by theramped surface 154 a. In contrast, sliding movement in the oppositedirection is restricted by vertical wall 156 a. Movement of segments 102a, 104 a is limited to a single direction with ratchetings 152 a ₁ andby limiting the separation of segments 102 a, 104 a along an axistransverse to the longitudinal axis of plate 100 a with fastener 106 aor 106 a′.

In a preferred embodiment, fastener 106 a or 106 a′ is configured tohave at least one position that permits movement of first and secondsegments 102 a, 104 a in both directions along the longitudinal axis ofplate 100 a as well as along an axis transverse to the longitudinal axisof plate 100 a such that ratchetings 152 a ₂ can move apart. Forexample, in a first position fastener 106 a can be less than fullytightened to plate 100 a as desired by the surgeon to permit movement offirst and second segments relative to each other. Fastener 106 a′ canfurther have a second position that permits movement of segments 102 a,104 a relative to one another only in a single direction along thelongitudinal axis of plate 100 a and limits movement along an axistransverse to the longitudinal axis of plate 100 a. Therefore, plate 100a can be shortened if the distance between the two adjacent vertebralbodies decreases, even after plate 100 a is installed, so that thevertebral bodies are not held apart by plate 100 a, to prevent theoccurrence of pseudoarthrosis. One of the benefits of a forward-facingconfiguration of ratchetings 152 a ₂ is the ability to store and imparta compressive load across the fusion site. The compressive load storedmay be applied by the surgeon and/or compressive loads that occurrandomly with neck motion during the healing phase. First and secondsegments 102 a, 104 a may be pre-adjusted to correspond to theappropriate size and spacing of the adjacent vertebral bodies to befused prior to placement of plate 100 a against the vertebral bodies bymoving first and second segments 102 a, 104 a relative to one anotherwhile fastener 106 a is only partially tightened for the purpose ofappropriately adjusting the length of the plate. Then, fastener 106 amay be further tightened to secure first and second segments 102 a, 104a in the desired position.

Plates 100 a and 100 b preferably include at least one bone screw lockadapted to lock to the plate only a single bone screw inserted into oneof the bone screw receiving holes. The plates of the present inventionmay include more than one bone screw lock, each lock being adapted tolock to the plate only a single bone screw inserted into one of the bonescrew receiving holes. Preferably, the bone screw lock physically blocksthe bone screw from unwanted loosening or unwanted backing out from theplate.

FIGS. 47 a–47 d show preferred embodiments of locking elements forlocking bone screws in accordance with the present invention. Forexample, the bone screw locks may be in the form of a screw, a rivet, acap, or a cover. It is appreciated that any locking element for lockinga single one of the bone screws known to one of ordinary skill in theart would be within the scope of the present invention.

FIG. 47 a shows an enlarged fragmentary cross sectional view of alocking element 172 a ₁ and a bone screw 174 a ₁. Locking element 172 a₁ threadably engages bone screw receiving hole 126 a to prevent bonescrew 174 a ₁ from backing out. In this embodiment, locking element 172a ₁ locks bone screw 174 a ₁ in a fixed relationship to plate 100 a.

FIG. 47 b is an enlarged fragmentary cross sectional view of a lockingelement 172 a ₂ and a bone screw 174 a ₂. Locking element 172 a ₂threadably engages bone screw receiving hole 126 a to prevent bone screw174 a ₂ from backing out. In this embodiment, locking element 172 a ₂ isadapted to hold bone screw 174 a ₂ in an angular relationship to plate100 a. Examples of preferred fixed-angled single locking elements aretaught by Michelson in U.S. Pat. No. 6,139,550, (the '550 patent)entitled “Skeletal Plating System,” the disclosure of which is herebyincorporated by reference herein. Locking element 172 a ₂ may alsopermit movement of bone screw 174 a ₂ relative to plate 100 a.

FIGS. 47 c and 47 d are enlarged fragmentary cross sectional views of alocking element 172 a ₃ and bone screw 174 a ₃ in accordance withanother embodiment of the present invention. Locking element 172 a ₃threadably engages bone screw receiving hole 126 a to prevent bone screw174 a ₃ from backing out. In this embodiment, locking element 172 a ₃ isadapted to hold bone screw 174 a ₃ in an angular relationship to plate100 a. Locking element 172 a ₃ may also permit movement of bone screw174 a ₃ relative to plate 100. Locking element 172 a ₃ is adapted toadjustably lock bone screw 174 a ₃ in a variable angle relationshiprelative to plate 100 a. Bone screw 174 a ₃ preferably has a roundedhead 176 a ₃ that cooperates with the bottom surface of single lockingelement 172 a ₃, thus allowing screw 174 a ₃ to move relative to plate100 a. Examples of preferred variable-angled single locking elements aretaught by Michelson in the '550 patent the disclosure of which is herebyincorporated by reference herein.

FIG. 47 e is an enlarged fragmentary cross sectional view of aself-locking bone screw 174 a ₄ in accordance with another embodiment ofthe present invention. Bone screw 174 a ₄ has thread 178 a ₄ adapted tothreadably engage bone screw receiving hole 126 a. The thread pattern ofthread 178 a ₄ is has a tighter pitch than the thread pattern of thebone engaging thread of bone screw 174 a ₄. The different thread pitchesprevent bone screw 174 a ₄ from backing out after installation iscompleted.

It is appreciated that various types of bone screws and single locksystems may be utilized with the plates of the present invention.

With appropriate embodiments of the plates described herein, the surgeonmay induce a desired amount of “preload,” or compressive force acrossthe fusion site after plate attachment by moving first and secondsegments 102 a, 104 a toward one another to shorten the length of plate100 as desired. Inducing a preload enhances fusion by maintaining acompressive force between adjacent vertebral bodies and reducing thechance that gaps might develop as new living bone replaces the dead boneduring the fusion process.

FIGS. 13A, 14A, and 15A show a preferred embodiment of instrumentation200 a for compressing and locking plate 100 a. Instrumentation 200 a hasa handle 202 a with a pair of tongs 204 a, 206 a in moveablerelationship to each. Tongs 204 a, 206 a are configured to cooperativelyengage ends 124 a, 144 a of first and second segments, 102 a, 104 a,respectively. Instrumentation 200 a may be used to hold and positionplate 100 a in a desired position at the fusion site during at least aportion of the procedure for installing plate 100 a. Any instrumentcapable of engaging the plate so as to serve the intended purpose wouldbe within the scope of the instrumentation and method of the presentinvention. As an example only, methods and instrumentation forinstalling plates to the cervical spine, including a pilot hole formingpunch to create bone screw receiving holes in the vertebral bodiescoaxially aligned with the bone screw receiving holes with the plate,are taught and described by Michelson in the '721 patent, incorporatedby reference herein. After segments 102 a, 104 a have been attached tothe adjacent vertebral bodies with an appropriate fastening element,such as bone screws, instrument 200 a can be used to move segments 102a, 104 a toward one another to shorten the length of plate 100 a andcreate a compressive load across the disc space. After the desiredlength of plate 100 a is achieved, an instrument 208 a having a head 210a configured to cooperatively engage fastener 106 a is used to tightenfastener 106 a to secure first and second segments 102 a, 104 a in adesired position. When in a secured position, segments 102 a, 104 a maymaintain a compressive load across the disc space if desired. Head 210 aof instrument 208 a may have a hex-shaped configuration.

FIGS. 1B, 2B, 4B, 7B, 8B, and 15B show another preferred embodiment of acervical plate 100 b in accordance with the present invention. In thispreferred embodiment of the present invention, plate 100 b may includeat least one bone screw lock adapted to lock to the plate only a singlebone screw inserted into one of bone screw receiving holes 126 b such asdescribed above in relation to plate 100 a and a non-detachable fastener106 b configured to couple together first and second segments 102 b, 104b. Fastener 106 b is configured to be non-detachably attached to atleast one of first and second segments 102 b, 104 b to couple togethertwo or more plate segments. Fastener 106 b is non-detachable to preventnon-destructive complete uncoupling of first and second segments 102 b,104 b from one another during normal use. As used herein,“non-detachable fastener” is defined as a fastener that once attached isnot meant to be removed and then reattached. As shown in FIG. 7B,fastener 106 b, for example, may be embodied in the form of a rivethaving a head 108 b, 0 a shaft 112 b, and a base 114 b. By way ofexample only and not limitation, base 114 b may be coupled to secondsegment 104 b so that it is permanently attached, but is still capableof an element of rotation about its longitudinal axis. Shaft 112 b offastener 106 b preferably has a thread 116 b.

Fastener receiving opening 148 b of plate 100 b is configured to permitnon-detachable attachment of fastener 106 b while permitting an elementof rotation of fastener 106 b about its longitudinal axis. For exampleas shown in FIG. 2B, the bottom portion of fastener receiving opening148 b proximate lower surface 140 b of second segment 104 b may have asmaller dimension than the maximum dimension of base 114 b (e.g. flaredportion of a rivet) of fastener 106 b so as to prevent passage of theend portion therethrough. Moreover, the bottom portion of fastenerreceiving opening 148 b may be beveled to accommodate base 114 b (e.g.flared portion) of fastener 106 b so that it is generally flush orrecessed to the bottom surface and preferably does not impede closecontact of lower surface 140 b with the surface of the vertebral bodies.The first and second plate segments may be modular components of variousconfigurations assembled by the manufacturer of the plate and providedto the surgeon in an assembled state. In the assembled state, the platehas a non-detachable fastener that prevents non-destructive completeuncoupling of the first and second segments during normal use.

FIGS. 1C, 2C, 3C, 4C, 6C, 13C, 14C, and 15C show another preferredembodiment of a cervical plate 100 c in accordance with the presentinvention. In this preferred embodiment of the present invention, plate100 c may include a detachable fastener configured to couple togetherfirst and second segments 102 c, 104 c such as described above inrelation to plate 100 a and a bone screw lock adapted to lock at leasttwo bone screws inserted in bone screw receiving holes 126 c. Bone screwlocks 172 c are coupled to plate 100 c and may be removable or may benon-detachably attached to plate 100 c. Bone screw locks 172 c may becoupled to plate 100 c prior to the insertion of the bone screws intobone screw receiving holes 126 c. Alternatively, the bone screw locksmay be coupled to the plate after the insertion of the bone screws intothe bone screw receiving holes.

As shown in FIGS. 1C, 2C, 3C,4C, 14C, and 15C, by way of example onlyand not limitation, bone screw lock 172 c may have a tool engagementportion 174 c adapted to cooperatively engage an instrument used forcoupling bone screw lock 172 c to plate 100 c and at least one cutout176 c. Each cutout 176 c is oriented so as to permit introduction of abone screw into an adjacent bone screw receiving hole when bone screwlock 172 c is coupled to plate 100 c and in the appropriate orientation.It is appreciated that other configurations of the bone screw lock arepossible so as to permit introduction of a bone screw into a bone screwreceiving hole adjacent to the bone screw lock without interference fromthe bone screw lock.

Plate 100 c may have an opening 178 c for receiving at least a portionof locking element 172 c and may, but need not, include a recess 180 cfor receiving at least a portion of locking element 172 c therein. Bonescrew lock 172 c may have a stem 182 c configured to fit at least inpart within opening 178 c in plate 100 c. Stem 182 c and opening 178 cmay be threaded to threadably engage bone screw lock 172 c to plate 100c. Alternatively, at least a portion of the interior perimeter of recess180 c and at least a portion of the perimeter of the bone screw lock maybe threaded to threadably engage the bone screw lock to the plate.

In a preferred embodiment, bone screw locks 172 c are configured to movefrom an initial position, that permits the insertion of bone screws intothe bone screw receiving holes, to a final position that is adapted toextend over at least a portion of at least two of the bone screws toretain the bone screws to the plate. The bone screw lock may be adaptedto be rotated from the initial position to the final position, andpreferably, less than a full rotation of the bone screw lock rotates thebone screw lock from the initial position to the final position. In apreferred embodiment, the bone screw lock in the final position coversat least a portion of at least two of the bone screw receiving holes.

In another preferred embodiment, at least a portion of the bone screwlock slides from the initial position to the final position. The bonescrew lock can slide over at least a portion of at least two of the bonescrew receiving holes and/or slide over at least a portion of at leasttwo bone screws in the bone screw receiving holes. The bone screw lockmay be in the form of a screw, a rivet, a cap, a cover, or have anyother configuration suitable for its intended purpose. The bone screwlock may have a head that is at least in part circular.

Where it is desired to lock more than one bone screw to the plate withone bone screw lock, any lock suitable for locking a plurality of bonescrews to an anterior cervical plate known to those of ordinary skill inthe art may be utilized, including but not limited to, the bone screwlocks taught by Michelson in U.S. Pat. No. 6,193,721 (the '721 patent),incorporated by reference herein.

FIGS. 1D, 2D, 4D, and 15D show another preferred embodiment of acervical plate 100 d in accordance with the present invention. In thispreferred embodiment of the present invention, plate 100 d may include anon-detachable fastener configured to couple together first and secondsegments 102 d, 104 d such as described above in relation to plate 100 band a bone screw lock adapted to lock at least two bone screws insertedinto bone screw receiving holes 126 d such as described above inrelation to plate 100 c.

FIGS. 16A, 17A, 18A, 19A, 20A, 21A, and 22A show another preferredembodiment of a cervical plate 300 a having an internal compressionmechanism in accordance with the present invention. Plate 300 a issimilar to plate 100 a except that fastener receiving opening 330 a andfastener 306 a function as part of a mechanism to move first and secondsegments 302 a, 304 a relative to one another to change the length ofplate 300 a to generate a compressive load across the disc space betweentwo adjacent vertebral bodies to be fused. Fastener receiving opening330 a includes instrument pin receiving recesses 362 a ₁ and 362 a ₂ forcooperating with the pin of an instrument 400 a (described below) formoving first and second segments 302 a, 304 a relative to one another.In addition, instead of a tab 136 a, plate 300 a has pins 358 a andtracks 360 a to maintain first and second segments 302 a, 304 a alignedalong the longitudinal axis of plate 300 a. Bone screw lock 372 a isadapted to lock to plate 300 a at least two bone screws inserted in bonescrew receiving holes 326 a.

As shown in FIGS. 20A, 21A, and 22A, first segment 302 a preferably hastwo pins 358 a depending therefrom for engagement in correspondingtracks 360 a in second segment 304 a. Pins 358 a slideably engage tracks360 a, respectively, and travel therein when first and second segments302 a, 304 a are moved relative to one another. Tracks 360 a arestaggered along the length of medial portion 342 a and pins 358 a arestaggered along the length of medial portion 322 a to maintain first andsecond segments 302 a, 304 a aligned along the longitudinal axis ofplate 300 a. It is appreciated that any plate configuration to achievethe intended purpose of maintaining first and second segments 302 a, 304a aligned along the longitudinal axis of the plate would be within thescope of the present invention.

FIGS. 23A, 24A, 25A, and- 26A show a preferred embodiment ofinstrumentation 400 a used for compressing and locking plate 300 a.Instrumentation 400 a has a working end 402 a configured tocooperatively engage fastener receiving opening 330 a and fastener 306a. After segments 302 a, 304 a have been attached to the adjacentvertebral bodies with an appropriate fastening element, such as bonescrews, instrument 400 a can be used to move segments 302 a, 304 atoward one another to shorten the length of plate 300 a, create acompressive load across the disc space, and concurrently tightenfastener 306 a (if desired) to secure first and second segments 302 a,304 a in a preferred position. Working end 402 a of instrument 400 apreferably has a driver portion 404 a configured to cooperatively engagedriver receiving opening 364 a in fastener 306 a. Driver portion 404 ais preferably hex-shaped. Working end 402 a preferably has a pin 406 aextending therefrom and displaced from driver portion 404 a to engageone of pin receiving recesses 362 a ₁ and 362 a ₂, respectively, whendriver portion 404 a is engaged with driver receiving opening 364 a infastener 306 a. With driver portion 404 a engaging fastener 306 a andpin 406 a inserted in pin receiving recess 362 a ₂ as shown in FIG. 25A,instrument 400 a rotates fastener 306 a in the direction of arrow A asshown in FIG. 26A to move first segment 302 a toward second segment 304a in the direction of arrow B to reduce the length of plate 300 a andcan if desired concurrently tighten fastener 306 a. The configuration ofplate 300 a provides for an internal compression mechanism that can beoperated by a driver instrument eliminating the need for an externallyapplied compression apparatus for shortening plate 300 a and creating acompressive load.

FIGS. 19B, 20B, 21B, 22B, and 24B show another preferred embodiment of acervical plate 300 b in accordance with the present invention similar toplate 300 a. In this preferred embodiment of the present invention,plate 300 b may include at least one bone screw lock adapted to lock tothe plate only a single bone screw inserted into one of bone screwreceiving holes 326 b such as described above in relation to plate 100 aand a non-detachable fastener 306 b configured to couple together firstand second segments 302 b, 304 b such as described above in relation toplate 100 b.

FIGS. 16C, 17C 18C, 19C, 21C, 22C, 23C, and 24C show another preferredembodiment of a cervical plate 300 c in accordance with the presentinvention similar to plate 300 a. In this preferred embodiment of thepresent invention, plate 300 c may include a detachable fastenerconfigured to couple together first and second segments 302 c, 304 csuch as described above in relation to plate 100 a and a bone screw lockadapted to lock at least two bone screws inserted in bone screwreceiving holes 326 c such as described above in relation to plate 100c.

FIGS. 19D, 21D, 22D, and 24D show another preferred embodiment of acervical plate 300 d in accordance with the present invention similar toplate 300 a. In this preferred embodiment of the present invention,plate 300 d may include a non-detachable fastener configured to coupletogether first and second segments 302 d, 304 d such as described abovein relation to plate 100 b and a bone screw lock adapted to lock atleast two bone screws inserted into bone screw receiving holes 326 dsuch as described above in relation to plate 100 c.

FIGS. 27A and 28A show another preferred embodiment of a cervical plate500 a in accordance with the present invention. Plate 500 a is similarto plate 100 a except that first segment 502 a is configured to receiveat least a portion of second segment 504 a therein in a tongue andgroove configuration. As shown in FIG. 28A, first segment 502 apreferably has a C-shaped cross section and second segment 504 apreferably has a T-shaped cross section. The configurations of segments502 a, 504 a in this embodiment of the present invention keep segments502 a, 504 a aligned along the longitudinal axis of plate 500 a andlimit movement of segments 502 a, 504 a in a direction generallytransverse to the longitudinal axis of plate 500 a. A person of ordinaryskill in the art would appreciate that other configurations ofcooperatively engaging first and second segments 502 a, 504 a arepossible without departing from the intended purpose within the broadscope of the present invention. Bone screw lock 572 a is adapted to lockto plate 500 a one bone screw inserted in one of bone screw receivingholes 526 a.

FIG. 27B shows another preferred embodiment of a cervical plate 500 b inaccordance with the present invention similar to plate 500 a. In thispreferred embodiment of the present invention, plate 500 b may includeat least one bone screw lock adapted to lock to the plate only a singlebone screw inserted into one of bone screw receiving holes 526 b such asdescribed above in relation to plate 100 a and a non-detachable fastener506 b configured to couple together first and second segments 502 b, 504b such as described above in relation to plate 100 b.

FIG. 27C shows another preferred embodiment of a cervical plate 500 c inaccordance with the present invention similar to plate 500 a. In thispreferred embodiment of the present invention, plate 500 c may include adetachable fastener configured to couple together first and secondsegments 502 c, 504 c such as described above in relation to plate 100 aand a bone screw lock adapted to lock at least two bone screws insertedin bone screw receiving holes 526 c such as described above in relationto plate 100 c.

FIG. 27D shows another preferred embodiment of a cervical plate 500 d inaccordance with the present invention similar to plate 500 a. In thispreferred embodiment of the present invention, plate 500 d may include anon-detachable fastener configured to couple together first and secondsegments 502 d, 504 d such as described above in relation to plate 100 band a bone screw lock adapted to lock at least two bone screws insertedinto bone screw receiving holes 526 d such as described above inrelation to plate 100 c.

FIGS. 29A, 30A, 31A, 32A, 33A, 34A, 35A, and -36A show another preferredembodiment of a cervical plate 600 a in accordance with the presentinvention. Plate 600 a is similar to plate 100 a except that it isconfigured for use across two levels of the cervical spine. In additionto the elements of plate 100 a, plate 600 a further includes anintermediate third segment 666 a between first and second segments 602a, 604 a. Third segment 666 a has a first end 668 a configured tocooperatively engage first segment 602 a. Third segment 666 a has asecond end 670 a configured to cooperatively engage second segment 604a. Third segment 666 a and first and second segments 602 a, 604 a arearticulated and can be moved to vary the spacing between the bone screwreceiving holes of the plate segments as well as the overall length ofthe plate. Third segment 666 a can be made of different lengths and/orconfigurations to vary the distance between first and second segments602 a, 604 a to further vary the spacing between the bone screwreceiving holes and further vary the overall length of the plate.

In a preferred embodiment of the present invention, plate 600 a could beprovided to the health care facility in a set of segments. For example,a set or group of six segments could include a longer and a shorter oneof first, second, and third segments 602 a, 604 a, 666 a. These segmentscould be assembled to cover a range of sizes. Additional intermediatesegments 666 a can be used to assemble a plate that covers additionallevels of the spine and preferably the spacing between plate segmentswould be adjustable.

First end 668 a of third segment 666 a has similar features to secondsegment 604 a including a fastener receiving recess 648 a, bone screwreceiving holes 626 a, ratchetings 652 a on at least a portion of itsupper surface 638 a, and a tab 636 a. Second end 670 a of third segment666 a has similar features to first segment 602 a including aratchetings 652 a on at least a portion of its lower surface 620 a and atab receiving recess 634 a. A first fastener 606 a couples togetherfirst segment 602 a to first end 668 a of third segment 666 a. A secondfastener couples together second segment 604 a to second end 670 a ofthird segment 666 a. Additional segments 666 a may be added for useacross more than two levels of the spine. Segments 666 a are configuredto be coupled together with first end 668 a of one segment 666 a tosecond end 670 a of another segment 666 a. Bone screw lock 672 a isadapted to lock to plate 600 a at least two bone screws inserted in bonescrew receiving holes 626 a.

FIGS. 37A, 38A, and- 39A show a preferred embodiment of instrumentation700 a for compressing and locking plate 600 a. Instrumentation 700 a hasa handle 702 a with a pair of tongs 704 a, 706 a in moveablerelationship to each. Tongs 704 a, 706 a are configured to cooperativelyengage ends 624 a, 644 a of first and second segments, 602 a, 604 a,respectively, to shorten the overall length of the plate and to apply adesired compressive load across multiple levels of the spine.Instrumentation 700 a may be used to position plate 600 a in a desiredposition at the fusion site during at least a portion of the procedurefor installing plate 600 a. An instrument may be used for holding theplate such as the instrumentation disclosed in the '721 patentincorporated by reference above. Instrument 700 a can be used to movesegments 602 a, 604 a toward one another and toward third segment 666 ato shorten the length of plate 600 a and create a compressive loadacross the respective disc spaces.

As shown in FIG. 38A, an alternative embodiment of instrument 700 a′ maybe used to move first or second segment 602 a, 604 a toward thirdsegment 666 a so that a compressive load may be applied to one discspace at a time. Instrument 700 a′ has a tong 704 a′ similar to tong 704a for engaging one of ends 624 a, 644 a of first and second segments 602a, 604 a, and forked tong 707 a for engaging the third segment as shownin FIG. 38A.

After the desired length of plate 600 a is achieved, an instrument 708 ahaving a head 710 a configured to cooperatively engage fastener 606 a isused to tighten fastener 606 a to secure first, second, and thirdsegments 602 a, 604 a, 666 a in a desired position.

FIGS. 30B, 31B, 33B, and 35B show another preferred embodiment of acervical plate 600 b in accordance with the present invention similar toplate 600 a. In this preferred embodiment of the present invention,plate 600 b may include at least one bone screw lock adapted to lock tothe plate only a single bone screw inserted into one of bone screwreceiving holes 626 b such as described above in relation to plate 100 aand a non-detachable fastener 606 b configured to couple together firstand second segments 602 b, 604 b such as described above in relation toplate 100 b.

FIGS. 29C, 30C, 31C, 32C, 33C, 34C, 35C, 36C, 37C, 38C, and 39C showanother preferred embodiment of a cervical plate 600 c in accordancewith the present invention similar to plate 600 a. In this preferredembodiment of the present invention, plate 600 c may include adetachable fastener configured to couple together first and secondsegments 602 c, 604 c such as described above in relation to plate 100 aand a bone screw lock adapted to lock at least two bone screws insertedin bone screw receiving holes 626 c such as described above in relationto plate 100 c.

FIGS. 30D, 31D, 33D, and 35D show another preferred embodiment of acervical plate 600 d in accordance with the present invention similar toplate 600 a. In this preferred embodiment of the present invention,plate 600 d may include a non-detachable fastener configured to coupletogether first and second segments 602 d, 604 d such as described abovein relation to plate 100 b and a bone screw lock adapted to lock atleast two bone screws inserted into bone screw receiving holes 626 dsuch as described above in relation to plate 100 c.

FIG. 40A shows another preferred embodiment of a cervical plate 800 a inaccordance with the present invention. Plate 800 a is similar to plate600 a except that first segment 802 a is configured to receive at leasta portion of the first end 868 a of third segment 866 a therein in atongue and groove configuration and second end 870 a of third segment866 a is configured to receive at least a portion of second segment 804a therein, in a tongue and groove configuration. A person of ordinaryskill in the art would appreciate that other configurations ofcooperatively engaging first and second segments 802 a, 804 a arepossible without departing from the intended purpose within the broadscope of the present invention. Bone screw lock 872 a is adapted to lockto plate 800 a at least two bone screws inserted in bone screw receivingholes 826 a.

FIG. 40B shows another preferred embodiment of a cervical plate 800 b inaccordance with the present invention similar to plate 800 a. In thispreferred embodiment of the present invention, plate 800 b may includeat least one bone screw lock adapted to lock to the plate only a singlebone screw inserted into one of bone screw receiving holes 826 b such asdescribed above in relation to plate 100 a and a non-detachable fastener806 b configured to couple together first and second segments 802 b, 804b such as described above in relation to plate 100 b.

FIG. 40C shows another preferred embodiment of a cervical plate 800 c inaccordance with the present invention similar to plate 800 a. In thispreferred embodiment of the present invention, plate 800 c may include adetachable fastener configured to couple together first and secondsegments 802 c, 804 c such as described above in relation to plate 100 aand a bone screw lock adapted to lock at least two bone screws insertedin bone screw receiving holes 826 c such as described above in relationto plate 100 c.

FIG. 40D shows another preferred embodiment of a cervical plate 800 d inaccordance with the present invention similar to plate 800 a. In thispreferred embodiment of the present invention, plate 800 d may include anon-detachable fastener configured to couple together first and secondsegments 802 d, 804 d such as described above in relation to plate 100 band a bone screw lock adapted to lock at least two bone screws insertedinto bone screw receiving holes 826 d such as described above inrelation to plate 100 c.

FIG. 41 shows a cervical plate 900 c with locking elements 902 c inaccordance with another preferred embodiment of the present invention.Locking elements 902 c are adapted to lock at least two bone screwsinstalled in each of bone screw receiving holes 916 c, respectively.Locking element 902 c is in moveable relationship to plate 900 c so thatlocking element 902 c can be pre-installed to plate 900 c prior to theinsertion of bone screws into bone screw receiving holes 916 c. Duringinstallation of the bone screws, locking element 902 c can be slid toone side of the plate as shown in the top portion of the plate in FIG.41 to allow for insertion of a first bone screw into a first bone screwreceiving hole 916 c on the opposite side of plate 900 c. Lockingelement 902 c is then moved to the opposite side of plate 900 c topermit insertion of a second bone screw into the second bone screwreceiving hole 916 c. Locking element 902 c is then moved to cover atleast a portion of both first and second bone screws and can be lockedin place by a screw 917 c as shown in the middle and bottom portions ofplate 900 c in FIG. 41.

FIGS. 42 and 43 show a cervical plate 1000 c with locking elements 1002c in accordance with another preferred embodiment of the presentinvention. Locking elements 1002 c are installed to cover at least aportion of two bone screw receiving holes 1016 c. In this embodiment,the bone screws are installed in bone screw receiving holes 1016 c andlocking element 1002 c is placed over at least a portion of two bonescrews to lock the bone screws. Locking element 1002 c can be held inplace with a screw 1017 c that passes at least in part through opening1003 c in locking element 1002 c and engages opening 1005 c in plate1000 c to lock two bone screws 1048 c to plate 1000 c as shown in FIG.43. Bone screws 1048 c preferably have a leading end configured forinsertion into the cervical spine and a head 1049 c opposite the leadingend that may be configured to contact locking element 1002 c. By way ofexample only, bone screws 1048 c may be configured to be in a fixedrelationship to plate 1000 c such as shown in FIG. 43.

FIG. 44 is a fragmentary cross sectional view of another preferredembodiment of a locking element 1002 c′ and bone screws 1048 c′. Lockingelement 1002 c′ has a bottom surface adapted to cooperate with a roundedportion of head 1049 c′ of bone screws 1048 c′ and is adapted to holdbone screws 1048 c′ in an angular relationship to plate 1000 c′.Examples of preferred fixed-angled locking elements are taught byMichelson the '550 patent hereby incorporated by reference herein.Locking element 1002 c′ may also permit movement of bone screw 1048 c′relative to plate 1000 c′. Locking element 1002 c′ may also be adaptedto adjustably lock bone screws 1048 c′ in a variable angle relationshiprelative to plate 1000 c′. Examples of preferred variable-angled lockingelements are taught by Michelson in the '550 patent. The rounded portionof head 1049 c′ permits bone screws 1048 c′ to be in a moveablerelationship, such as for example in a variable angular relationship toplate 1000 c′. Other configurations are possible for the intendedpurpose and are within the broad scope of the present invention.

Various methods for using and installing the plates of the presentinvention are disclosed in the '550 and '721 patents to Michelsonidentified above, incorporated by reference herein.

FIG. 45 shows a plate 1100 c and a locking element 1180 c adapted tolock at least two bone screws and a fastener 1134 c in accordance withthe present invention. Preferably, locking element 1180 c is configuredto be preinstalled to plate 1100 c prior to insertion of the bone screwsin bone screw receiving holes 1116 c and attachment of fastener 1134 cto plate 1100 c. Locking element 1180 c has a first position thatpermits insertion of bone screws in respective bone screw receivingholes 1116 c and installation and/or movement of fastener 1134 c.Locking element 1180 c has a second position that covers at least aportion of at least two bone screw receiving holes 1116 c and fastener1134 c to lock at least two bone screws and fastener 1134 c to plate1100 c. Locking element 1180 c may preferably be configured to rotatablyand/or slideably cover at least a portion of two bone screws in bonescrew receiving holes 1116 c and at least a portion of fastener 1134 c.

FIG. 46 shows another preferred embodiment of a plate 1200 c and lockingelement 1280 c adapted to lock at least two bone screws and a fastener1234 c in accordance with the present invention. Locking element 1280 cis configured to be installed to plate 1200 c after insertion of bonescrews in bone screw receiving holes 1216 c and attachment of fastener1234 c to plate 1200 c. Locking element 1280 c is configured to cover atleast a portion of at least two bone screw receiving holes 1216 c andfastener 1234 c to lock at least two bone screws and at least a portionof fastener 1234 c to plate 1200 c. Locking element 1280 c is preferablyattached to plate 1200 c by a screw 1217 c or by any other meanssuitable for the intended purpose.

The plates of present invention may include a bone screw system thatallows the vertebrae to move toward an interposed bone graft, and eachother if necessary, instead of keeping the vertebrae apart during theoccurrence of the resorption phase of the creeping substitution process.For example, the '550 patent discloses three types of screw-plate-locksystems, which are themselves combinable with one another, as follows:(1) Passive Dynamic; (2) Self-Compressing; and (3) Active Dynamic andare incorporated by reference herein.

It is appreciated that for any of the embodiments of the platesdescribed herein can be made of, treated, coated, combined with,comprised of, or used with any source of osteogenesis, fusion promotingsubstances, bone growth promoting materials, bone, bone derivedsubstances or products, demineralized bone matrix, mineralizingproteins, ossifying proteins, bone morphogenetic proteins,hydroxyapatite, genes coding for the production of bone, substancesother than bone, and bone including, but not limited to, cortical bone.The plates, screws, fasteners, and/or screw locks may also be combinedwith material and/or substance for inhibiting scar formation. Theplates, screws, fasteners, and/or screw locks may be combined with anantimicrobial material and/or surface treated or coated to beantibacterial and/or antimicrobial, such as for example, by a silvercoating. At least a portion of the bottom surface of the plates canpreferably have a porous, and/or textured and/or roughened surface andmay be coated with, impregnated with, or comprise of fusion promotingsubstances (such as bone morphogenetic proteins) so as to encourage thegrowth of bone along the underside of the plate from bone portion tobone portion. The textured bottom surface also provides a medium forretaining fusion promoting substances with which the bottom surfacelayer can be impregnated prior to installation. The bottom surface ofthe plate may be given the desired porous textured form by roughblasting or any other conventional technology, such as etching, plasmaspraying, sintering, and casting for example. If porous so as to promotebone ingrowth, the bottom surface is formed to have a porosity or poresize in the order of 50–500 microns, and preferably 100–300 microns.Bone growth promoting substances with which the porous, textured bottomsurface can be impregnated include, but are not limited to, bonemorphogenetic proteins, hydroxyapatite, or hydroxyapatite tricalciumphosphate. The plate, screws, fasteners, and/or bone screw locks mayinclude at least in part a resorbable and/or bioresorbable materialwhich can further be impregnated with a bone growth material so that asthe resorbable and/or bioresorbable material is resorbed by the body ofthe patient, the bone growth material is released, thus acting as a timerelease mechanism. The bioresorbable material may be, for example, atleast in part bone. The plate of the present invention may be used incombination with a spinal fixation implant such as any object,regardless of material, that can be inserted into any portion of thespine, such as but not limited to interbody spinal implants, interbodyspinal fusion implants, structural bone grafts, mesh, cages, spacers,staples, bone screws, plates, rods, tethers of synthetic cords or wires,or other spinal fixation hardware. The interbody spinal fusion implantsmay be at least in part bone, for example only, an allograft interbodybone graft. Alternatively, the spinal interbody spinal fusion implantmay be at least in part artificial. At least one of the plate, screws,fasteners, and/or bone screw locks may be, if so desired, electrifiedfor purposes of stimulating bone growth and contributing to bone fusion.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A plate adapted to be applied to the anterior human cervical spinefor contacting the anterior aspects of at least two adjacent cervicalvertebral bodies to be fused together, said plate comprising: at least afirst plate segment adapted to be attached to one of the adjacentvertebral bodies to be fused and at least a second plate segment adaptedto be attached to another one of the adjacent vertebral bodies to befused, said at least first and second plate segments adapted to beconnected to one another and at least in part overlapped to form saidplate, said at least first and second plate segments being in a moveablerelationship to one another along a longitudinal axis of said plate,each of said at least first and second plate segments including: a lowersurface adapted to contact at least one of the cervical vertebral bodiesand an upper surface opposite said lower surface said lower surfacebeing concave at least In part along at least a portion of thelongitudinal axis of said plate; at least one bone screw receiving holeextending from said upper surface through said lower surface, each ofsaid bone screw receiving holes adapted to overlie one of the cervicalvertebral bodies and being adapted to receive at least one bone screwfor engaging the cervical vertebral body to attach said plate to thecervical spine; said first and second plate segments being configured tocouple together in cooperative relationship so as to facilitate movementof said first and second plate segments in a direction toward oneanother along the longitudinal axis of said plate and to resist movementof said first and said second plate segments in a direction away fromone another along the longitudinal axis of said plate, said first andsecond plate segments when attached to the ad scent vertebral bodies,respectively, being adapted to move toward one another in response tomovement of the adjacent vertebral bodies toward each other.
 2. Theplate of claim 1, wherein said first and second plate segments areconfigured to limit movement of said first and second plate segmentsrelative to one another along the longitudinal axis of said plate. 3.The plate of claim 1, wherein said first and second plate segments areconfigured so as to be able to completely restrict movement of saidfirst and second plate segments relative to one another along at least alongitudinal axis of said plate.
 4. The plate of claim 1, wherein saidfirst and second plate segments are configured so as to limit separationof said first and second plate segments relative to one another whencoupled together.
 5. The plate of claim 1, wherein at least one of saidfirst and second plate segments is configured to receive at least aportion of another one of said first and second plate segments therein.6. The plate of claim 5, wherein at least one of said first and secondplate segments has a projection and at least one of said first andsecond plate segments has a groove configured to receive at least aportion of said projection.
 7. The plate of claim 1, wherein said firstand second plate segments when attached to the adjacent vertebralbodies, respectively, are adapted to maintain a compressive load acrossa disc space between the adjacent cervical vertebral bodies.
 8. Theplate of claim 1, wherein at least a portion of said upper surface ofsaid second plate segment is convex at least in part along at least aportion of the longitudinal axis of said plate.
 9. The plate of claim 1,wherein said at least first and second plate segments are configured tocooperate so as to maintain said first and second plate segmentsgenerally aligned along the longitudinal axis of said plate.
 10. Theplate of claim 1, wherein said at least first and second plate segmentsare configured to cooperate so as to limit movement of said first andsecond plate segments in a direction generally transverse to thelongitudinal axis of said plate.
 11. The plate of claim 1, wherein atleast a portion of said lower surface of said first plate segment isconfigured to cooperatively engage at least a portion of said uppersurface of said second plate segment.
 12. The plate of claim 1, whereinat least a portion of said lower surface of said first plate segment isconfigured to interdigitate with at least a portion of said uppersurface of said second plate segment.
 13. The plate of claim 12, whereinsaid at least a portion of said lower surface of said first platesegment and said at least a portion of said upper surface of said secondplate segment include at least one ratchet.
 14. The plate of claim 1,wherein at least one of said first and second plate segments is selectedfrom a group of plate segments of various lengths.
 15. The plate ofclaim 1, wherein at least one of said first and second plate segments isselected from a group of plate segments of various configurations. 16.The plate of claim 1, further comprising at least a third plate segmentadapted to be connected to at least one of said first and second platesegments to form said plate.
 17. The plate of claim 16, wherein saidthird plate segment is an intermediate plate segment configured to becoupled between at least two plate segments.
 18. The plate of claim 16,wherein at least one of said first, second, and third plate segments isselected from a group of plate segments of various lengths.
 19. Theplate of claim 16, wherein at least one of said first, second, and thirdplate segments is selected from a group of plate segments of variousconfigurations.
 20. The plate of claim 19, wherein said first, second,and third plate segments are selected from a group including endsegments and intermediary segments.
 21. The plate of claim 20, whereineach of said end segments is configured to connect to one of said endsegments and said intermediary segments, and each of said intermediarysegments is configured to connect to at least one of said end segmentsand said intermediary segments.
 22. The plate of claim 1, furthercomprising at least one bone screw, at least one of said first andsecond plate segments and said bone screw cooperate to lock to saidplate said at least one bone screw inserted in said bone screw receivingholes, respectively.
 23. The plate of claim 1, further comprising atleast one bone screw lock adapted to lock to said plate at least onebone screw inserted in said bone screw receiving holes, respectively.24. The plate of claim 23, wherein said at least one bone screw lock iscoupled to said plate.
 25. The plate of claim 24, wherein said at leastone bone screw lock is removably coupled to said plate.
 26. The plate ofclaim 24, wherein said at least one bone screw lock is adapted to becoupled to said plate prior to the insertion of at least one bone screwinto at least one of said bone screw receiving holes.
 27. The plate ofclaim 23, wherein said at least one bone screw lock is configured tomove from an initial position that permits the insertion of at least onebone screw into at least one of said bone screw receiving holes to afinal position that is adapted to extend over at least a portion of atleast one of the bone screws to retain the bone screw to said plate. 28.The plate of claim 27, wherein said at least one bone screw lock in thefinal position covers at least a portion of at least one of said bonescrew receiving holes.
 29. The plate of claim 27, wherein said at leastone bone screw lock is adapted to be rotated from the initial positionto the final position.
 30. The plate of claim 29, wherein less than afull rotation of said at least one bone screw lock rotates said bonescrew lock from the initial position to the final position.
 31. Theplate of claim 27, wherein at least a portion of said at least one bonescrew lock slides from the initial position to the final position. 32.The plate of claim 31, wherein said at least one bone screw lock slidesover at least a portion of at least one of said bone screw receivingholes.
 33. The plate of claim 32, wherein said at least one bone screwlock slides over at least a portion of at least one bone screw in atleast one of said bone screw receiving holes.
 34. The plate of claim 23,wherein said at least one bone screw lock comprises at least one of ascrew, a rivet, a cap, and a cover.
 35. The plate of claim 23, whereinsaid at least one bone screw lock comprises a head that is at least inpart circular.
 36. The plate of claim 35, wherein said head has at leastone cutout segment.
 37. The plate of claim 23, further comprising atleast one fastener adapted to couple together said first and secondplate segments and wherein said at least one bone screw lock is adaptedto lock to said plate said at least one fastener.
 38. The plate of claim37, wherein said at least one bone screw lock covers at least a portionof at least one of said bone screw receiving holes and at least aportion of said at least one fastener.
 39. The plate of claim 37,wherein said at least one bone screws lock slides over at least aportion of at least one bone screw in at least one of said bone screwreceiving holes and at least a portion of said at least one fastener.40. The plate of claim 1, further comprising at least one fasteneradapted to fasten together said first and second plate segments.
 41. Theplate of claim 40, wherein said fastener is detachably attached to atleast one of said first and second plate segments so as to permitassembly of said first and second plate segments by the surgeon andcomplete uncoupling of said first and second plate segments relative toone another.
 42. The plate of claim 40, wherein said fastener isnon-detachably attached to at least one of said first and second platesegments so as to prevent complete uncoupling of said first and secondplate segments relative to one another.
 43. The plate of claim 40,wherein said fastener has a first position adapted to facilitatemovement of said first and second plate segments in a direction towardone another along the longitudinal axis of said plate and to resistmovement of said first and said second plate segments in a directionaway from one another along the longitudinal axis of said plate.
 44. Theplate of claim 43, wherein said first and second plate segments move inonly a single direction toward one another along the longitudinal axisof said plate when said fastener is in said first position.
 45. Theplate of claim 43, wherein said fastener has a second position adaptedto limit movement of said first and second plate segments relative toone another along the longitudinal axis of said plate.
 46. The plate ofclaim 40, wherein said fastener is configured so as to be able tocompletely restrict movement of said first and second plate segmentsrelative to one another along at least a longitudinal axis of saidplate.
 47. The plate of claim 40, wherein said fastener passes throughat least a portion of said first and second plate segments.
 48. Theplate of claim 40, wherein said fastener is configured to limitseparation of said first and second plate segments relative to oneanother.
 49. The plate of claim 40, wherein said fastener is configuredto be tightened to only one of said at least first and second platesegments so as to permit movement of said first and second platesegments relative to one another.
 50. The plate of claim 40, whereinsaid fastener is a part of a mechanism for moving said first and secondplate segments relative to one another along a longitudinal axis of saidplate.
 51. The plate of claim 40, in combination with an instrumentconfigured to cooperatively engage said fastener and at least a portionof at least one of said first and second plate segments so as uponmovement of said fastener with said instrument said first and secondplate segments move relative to one another along a longitudinal axis ofsaid plate.
 52. The plate of claim 51, wherein said fastener isconfigured to be rotated at least in part by said instrument.
 53. Theplate of claim 40, wherein said fastener is a screw.
 54. The plate ofclaim 40, where said fastener is at least in part threaded.
 55. Theplate of claim 40, wherein said fastener has a head.
 56. The plate ofclaim 50, wherein said fastener has a shaft.
 57. The plate of claim 1,wherein at least one end of said plate is configured to cooperativelyengage a compression tool for movement of at least one vertebral bodytoward another vertebral body during installation of said plate.
 58. Theplate of claim 1, wherein said concave part of said lower surface ofsaid first and second plate segment is configured to conform to theanterior aspect of at least a portion of two cervical vertebral bodies.59. The plate of claim 1, wherein at least a portion of said lowersurface of said first and second plate segment is at least in partconcave transverse to the longitudinal axis of the plate.
 60. The plateof claim 1, wherein at least a portion of said lower surface of saidfirst and second plate segments is roughened to promote the growth ofbone along said lower surface.
 61. The plate of claim 1, wherein atleast a portion of said lower surface of said first and second platesegments comprises a bone ingrowth surface.
 62. The plate of claim 1,wherein at least one of said bone screw receiving holes is configured toform an interference fit with at least a portion of the trailing end ofa properly dimensioned bone screw to be received therein.
 63. The plateof claim 1, wherein at least one of said bone screw receiving holes isconfigured to hold a bone screw in fixed relationship to said plate. 64.The plate of claim 1, wherein at least one of said bone screw receivingholes is configured to allow a bone screw to be in a moveablerelationship to said plate.
 65. The plate of claim 1, wherein at leastone of said bone screw receiving holes is configured to allow a bonescrew to be in a variable angular relationship to said plate.
 66. Theplate of claim 1, in combination with a fusion promoting substance. 67.The plate of claim 66, wherein said fusion promoting substance is atleast in part other than bone.
 68. The plate of claim 66, wherein saidfusion promoting substance is at least in part bone.
 69. The plate ofclaim 66, wherein said fusion promoting substance is hydroxyapatite. 70.The plate of claim 66, wherein said fusion promoting substance comprisesbone morphogenetic protein.
 71. The plate of claim 66, wherein saidfusion promoting substance comprises genes coding for the production ofbone.
 72. The plate of claim 1, in combination with a substance forinhibiting scar formation.
 73. The plate of claim 1, in combination withan antimicrobial material.
 74. The plate of claim 1, wherein said plateis treated with an antimicrobial material.
 75. The plate of claim 1,wherein said plate is electrified for purposes of stimulating bonegrowth and contributing to bone fusion.
 76. The plate of claim 40,wherein at least one of said plate and said fastener is electrified forpurposes of stimulating bone growth and contributing to bone fusion. 77.The plate of claim 23, further comprising at least one bone screw havinga leading end for insertion into the cervical spine and a head oppositesaid leading end, said at least one bone screw lock adapted to contactsaid head.
 78. The plate of claim 77, wherein said at least one bonescrew is configured to be in fixed relationship to said plate.
 79. Theplate of claim 77, wherein said at least one bone screw is configured tobe in a moveable relationship to said plate.
 80. The plate of claim 77,wherein at least one bone screw is configured to be in a variableangular relationship to said plate.
 81. The plate of claim 77, whereinat least one of said bone screw receiving holes has a reduced dimensionproximate said lower surface of said plate to form a seat, said seathaving a substantially planar surface adapted to contact a lower surfaceof one of said bone screws.
 82. A plate adapted to be applied to theanterior human cervical spine for contacting the anterior aspects of atleast two adjacent cervical vertebral bodies to be fused together, saidplate comprising: at least a first plate segment adapted to be attachedto one of the adjacent vertebral bodies to be fused and at least asecond plate segment adapted to be attached to another one of theadjacent vertebral bodies to be fused, said at least first and secondplate segments adapted to be connected to one another and at least inpart overlapped to form said plate, said at least first and second platesegments being in a moveable relationship to one another along alongitudinal axis of said plate, each of said at least first and secondplate segments including: a lower surface adapted to contact at leastone of the cervical vertebral bodies and an upper surface opposite saidlower surface, said lower surface being concave at least in part alongat least a portion of the longitudinal axis of said plate, at least aportion of said lower surface of said first plate segment is configuredto interdigitate with at least a portion of said upper surface of saidsecond plate segment; at least one bone screw receiving hole extendingfrom said upper surface through said lower surface, each of said bonescrew receiving holes adapted to overlie one of the cervical vertebralbodies and being adapted to receive at least one bone screw for engagingthe cervical vertebral body to attach said plate to the cervical spine;said first and second plate segments being configured to couple togetherin cooperative relationship so as to move in only a single directiontoward one another along the longitudinal axis of said plate.
 83. Theplate of claim 82, wherein sad first and second plate segments areconfigured to limit movement of said first and second plate segmentsrelative to one another along the longitudinal axis of said plate. 84.The plate of claim 82, wherein said first and second plate segments whenattached to the adjacent vertebral bodies, respectively, are adapted tomove toward one another in response to movement of the adjacent cervicalvertebral bodies toward each other.
 85. The plate of claim 82, whereinsaid first and second plate segments when attached to the adjacentvertebral bodies, respectively, are adapted to move the adjacentcervical vertebral bodies toward each other in response to movement ofsaid first and second plate segments moving toward each other.
 86. Theplate of claim 82, wherein said first and second plate segments whenattached to the adjacent vertebral bodies, respectively, are adapted tomaintain a compressive load across a disc space between the adjacentcervical vertebral bodies.
 87. The plate of claim 82, further comprisingat least one bone screw lock adapted to lock to said plate at least onebone screw inserted in said bone screw receiving holes, respectively.88. The plate of claim 87, wherein said at least one bone screw lockcomprises at least one of a screw, a rivet, a cap, and a cover.
 89. Theplate of claim 82, further comprising at least one fastener adapted tofasten together said first and second plate segments.
 90. The plate ofclaim 82, in combination with a fusion promoting substance.
 91. Theplate of claim 90, wherein said fusion promoting substance includes atleast one of bone, hydroxyapatite, bone morphogenetic protein, and genescoding for the production of bone.
 92. The plate of claim 82, furthercomprising bone screws for engaging said plate to the cervical spine,wherein at least a portion of one of said plate and said bone screws isa bioresorbable material.
 93. The plate of claim 82, in combination witha substance for inhibiting scar formation.
 94. The plate of claim 82, incombination with an antimicrobial material.
 95. A plate adapted to beapplied to the anterior human cervical spine for contacting the anterioraspects of at least two adjacent cervical vertebral bodies to be fusedtogether, said plate comprising: at least a first plate segment adaptedto be attached to one of the adjacent vertebral bodies to be fused andat least a second plate segment adapted to be attached to another one ofthe adjacent vertebral bodies to be fused, said at least first andsecond plate segments adapted to be connected to one another and atleast in part overlapped to form said plate, said at least first andsecond plate segments being in a moveable relationship to one anotheralong a longitudinal axis of said plate, each of said at least first andsecond plate segments including: a lower surface adapted to contact atleast one of the cervical vertebral bodies and an upper surface oppositesaid lower surface, said lower surface being concave at least in partalong at least a portion of the longitudinal axis of said plate, atleast a portion of said upper surface of said second plate segment beingconvex at least in part along at least a portion of the longitudinalaxis of said plate, said concave lower surface of said first platesegment having a radius of curvature that is different than the radiusof curvature of said convex upper surface of said second plate segment;at least one bone screw receiving hole extending from said upper surfacethrough said lower surface, each of said bone screw receiving holesadapted to overlie one of the cervical vertebral bodies and beingadapted to receive at least one bone screw for engaging the cervicalvertebral body to attach said plate to the cervical spine; said firstand second plate segments being configured to couple together incooperative relationship so as to facilitate movement of said first andsecond plate segments in a direction toward one another along thelongitudinal axis of said plate and to resist movement of said first andsaid second plate segments in a direction away from one another alongthe longitudinal axis of said plate.
 96. The plate of claim 95, whereinsaid first and second plate segments are configured to limit movement ofsaid first and second plate segments relative to one another along thelongitudinal axis of said plate.
 97. The plate of claim 95, wherein saidfirst and second plate segments when attached to the adjacent vertebralbodies, respectively, are adapted to move toward one another in responseto movement of the adjacent cervical vertebral bodies toward each other.98. The plate of claim 95, wherein said first and second plate segmentswhen attached to the adjacent vertebral bodies, respectively, areadapted to move the adjacent cervical vertebral bodies toward each otherin response to movement of said first and second plate segments movingtoward each other.
 99. The plate of claim 95, wherein said first andsecond plate segments when attached to the adjacent vertebral bodies,respectively, are adapted to maintain a compressive load across a discspace between the adjacent cervical vertebral bodies.
 100. The plate ofclaim 95, further comprising at least one bone screw lack adapted tolock to said plate at least one bone screw inserted in said bone screwreceiving holes, respectively.
 101. The plate of claim 100, wherein saidat least one bone screw lock comprises at least one of a screw, a rivet,a cap, and a cover.
 102. The plate of claim 95, further comprising atleast one fastener adapted to fasten together said first and secondplate segments.
 103. The plate of claim 95, in combination with a fusionpromoting substance.
 104. The plate of claim 103, wherein said fusionpromoting substance includes at least one of bone, hydroxyapatite, bonemorphogenetic protein, and genes coding for the production of bone. 105.The plate of claim 95, further comprising bone screws for engaging saidplate to the cervical spine, wherein at least a portion of one of saidplate and said bone screws is a bioresorbable material.
 106. The plateof claim 95, in combination with a substance for inhibiting scarformation.
 107. The plate of claim 95, in combination with anantimicrobial material.
 108. A plate adapted to be applied to theanterior human cervical spine for contacting the anterior aspects of atleast two adjacent cervical vertebral bodies to be fused together, saidplate comprising: at least a first plate segment adapted to be attachedto one of the adjacent vertebral bodies to be fused and at least asecond plate segment adapted to be attached to another one of theadjacent vertebral bodies to be fused, said at least first and secondplate segments adapted to be connected to one another and at least inpart overlapped to form said plate, said at least first and second platesegments being in a moveable relationship to one another along alongitudinal axis of said plate, each of said at least first and secondplate segments including: a lower surface adapted to contact at leastone of the cervical vertebral bodies and an upper surface opposite saidlower surface, said lower surface being concave at least in part alongat least a portion of the longitudinal axis of said plate, at least aportion of said lower surface of said first plate segment beingconfigured to interdigitate with at least a portion of said uppersurface of said second plate segment, said at least a portion of saidlower surface of said first plate segment and said at least a portion ofsaid upper surface of said second plate segment including at least oneratchet configured to permit movement of said first and second platesegments toward one another in a first direction along a longitudinalaxis of said plate and to restrict movement in a direction opposite tosaid first direction; at least one bone screw receiving hole extendingfrom said upper surface through said lower surface, each of said bonescrew receiving holes adapted to overlie one of the cervical vertebralbodies and being adapted to receive at least one bone screw for engagingthe cervical vertebral body to attach said plate to the cervical spine;said first and second plate segments being configured to couple togetherin cooperative relationship so as to facilitate movement of said firstand second plate segments in a direction toward one another along thelongitudinal axis of said plate and to resist movement of said first andsaid second plate segments in a direction away from one another alongthe longitudinal axis of said plate.
 109. The plate of claim 108,wherein said first and second plate segments when attached to theadjacent vertebral bodies, respectively, are adapted to move toward oneanother in response to movement of the adjacent cervical vertebralbodies toward each other.
 110. The plate of claim 108, wherein saidfirst and second plate segments when attached to the adjacent vertebralbodies, respectively, are adapted to move the adjacent cervicalvertebral bodies toward each other in response to movement of said firstand second plate segments moving toward each other.
 111. The plate ofclaim 108, wherein said first and second plate segments when attached tothe adjacent vertebral bodies, respectively, are adapted to maintain acompressive load across a disc space between the adjacent cervicalvertebral bodies.
 112. The plate of claim 108, further comprising atleast one bone screw lock adapted to lock to said plate at least onebone screw inserted in said bone screw receiving holes, respectively.113. The plate of claim 112, wherein said at least one bone screw lockcomprises at least one of a screw, a rivet, a cap, and a cover.
 114. Theplate of claim 108, further comprising at least one fastener adapted tofasten together said first and second plate segments.
 115. The plate ofclaim 108, in combination with a fusion promoting substance.
 116. Theplate of claim 115, wherein said fusion promoting substance includes atleast one of bone, hydroxyapatite, bone morphogenetic protein, and genescoding for the production of bone.
 117. The plate of claim 108, furthercomprising bone screws for engaging said plate to the cervical spine,wherein at least a portion of one of said plate and said bone screws isa bioresorbable material.
 118. The plate of claim 108, in combinationwith a substance for inhibiting scar formation.
 119. The plate of claim108, in combination with an antimicrobial material.
 120. A systemadapted to be applied to the anterior human cervical spine forcontacting the anterior aspects of at least two adjacent cervicalvertebral bodies to be fused together, said system comprising: a platecomprising: at least a first plate segment adapted to be attached to oneof the adjacent vertebral bodies to be fused and at least a second platesegment adapted to be attached to another one of the adjacent vertebralbodies to be fused, said at least first and second plate segmentsadapted to be connected to one another and at least in part overlappedto form said plate, said at least first and second plate segments beingin a moveable relationship to one another along a longitudinal axis ofsaid plate, each of said at least first and second plate segmentsincluding: a lower surface adapted to contact at least one of thecervical vertebral bodies and an upper surface opposite said lowersurface, said lower surface being concave at least in part along atleast a portion of the longitudinal axis of said plate; at least onebone screw receiving hole extending from said upper surface through saidlower surface, each of said bone screw receiving holes adapted tooverlie one of the cervical vertebral bodies and being adapted toreceive at least one bone screw for engaging the cervical vertebral bodyto attach said plate to the cervical spine; said first and second platesegments being configured to couple together in cooperative relationshipso as to facilitate movement of said first and second plate segments ina direction toward one another along the longitudinal axis of said plateand to resist movement of said first and said second plate segments in adirection away from one another along the longitudinal axis of saidplate; an interbody spinal fusion implant; and a fusion promotingsubstance.
 121. The plate of claim 120, wherein said first and secondplate segments are configured to limit movement of said first and secondplate segments relative to one another along the longitudinal axis ofsaid plate.
 122. The plate of claim 120, wherein said first and secondplate segments when attached to the adjacent vertebral bodies,respectively, are adapted to move toward one another in response tomovement of the adjacent cervical vertebral bodies toward each other.123. The plate of claim 120, wherein said first and second platesegments when attached to the adjacent vertebral bodies, respectively,are adapted to move the adjacent cervical vertebral bodies toward eachother in response to movement of said first and second plate segmentsmoving toward each other.
 124. The plate of claim 120, wherein saidfirst and second plate segments when attached to the adjacent vertebralbodies, respectively, are adapted to maintain a compressive load acrossa disc space between the adjacent cervical vertebral bodies.
 125. Theplate of claim 120, further comprising at least one bone screw lockadapted to lock to said plate at least one bone screw inserted in saidbone screw receiving holes, respectively.
 126. The plate of claim 125,wherein said at least one bone screw lock comprises at least one of ascrew, a rivet, a clip, and a cover.
 127. The plate of claim 120,further comprising at least one fastener adapted to fasten together saidfirst and second plate segments.
 128. The plate of claim 120, whereinsaid fusion promoting substance includes at least one of bone,hydroxyapatite, one morphogenetic protein, and genes coding for theproduction of bone.
 129. The plate of claim 120, further comprising bonescrews for engaging said plate to the cervical spine, wherein at least aportion of one of said plate and said bone screws is a bioresorbablematerial.
 130. The plate of claim 120, in combination with a substancefor inhibiting scar formation.
 131. The plate of claim 120, incombination with an antimicrobial material.
 132. The plate of claim 120,wherein said implant comprises at least in part bone.
 133. The plate ofclaim 120, wherein said implant is an allograft interbody bone graftimplant.
 134. The plate of claim 120, wherein said implant is anartificial implant.
 135. A system adapted to be applied to the anteriorhuman cervical spine for contacting the anterior aspects of at least twoadjacent cervical vertebral bodies to be fused together, said systemcomprising: a plate comprising: at least a first plate segment adaptedto be attached to one of the adjacent vertebral bodies to be fused andat least a second plate segment adapted to be attached to another one ofthe adjacent vertebral bodies to be fused, said at least first andsecond plate segments adapted to be connected to one another and atleast in part overlapped to form said plate, said at least first andsecond plate segments being in a moveable relationship to one anotheralong a longitudinal axis of said plate, each of said at least first andsecond plate segments including: a lower surface adapted to contact atleast one of the cervical vertebral bodies and an upper surface oppositesaid lower surface said lower surface being concave at least in partalong at least a portion of tile longitudinal axis of said plate; atleast one bone screw receiving hole extending from said upper surfacethrough said lower surface, each of said bone screw receiving holesadapted to overlie one of the cervical vertebral bodies and beingadapted to receive at least one bone screw for engaging the cervicalvertebral body to attach said plate to the cervical spine; said firstand second plate segments being configured to couple together incooperative relationship so as to facilitate movement of said first andsecond plate segments in a direction toward one another along thelongitudinal axis of said plate and to resist movement of said first andsaid second plate segments in a direction away from one another alongthe longitudinal axis of said plate, said first and second platesegments when attached to the adjacent vertebral bodies, respectively,being adapted to move toward one another in response to of the adjacentcervical vertebral bodies toward each other; and bone screws forengaging said plate to the cervical spine, wherein at least a portion ofone of said plate and said bone screws is a bioresorbable material. 136.The plate of claim 135, wherein said first and second plate segments areconfigured to limit movement of said first and second plate segmentsrelative to one another along the longitudinal axis of said plate. 137.The plate of claim 135, wherein said first and second plate segmentswhen attached to the adjacent vertebral bodies, respectively, areadapted to maintain a compressive load across a disc space between theadjacent cervical vertebral bodies.
 138. The plate of claim 135, furthercomprising at least one bone screw lock adapted to lock to said plate atleast one bone screw inserted in said bone screw receiving holes,respectively.
 139. The plate of claim 138, wherein said at least onebone screw lock composes at least one of a screw, a rivet, a cap, and acover.
 140. The plate of claim 135, further comprising at least onefastener adapted to fasten together said first and second platesegments.
 141. The plate of claim 135, in combination with a fusionpromoting substance.
 142. The plate of claim 141, wherein said fusionpromoting substance includes at least one of bone, hydroxyapatite, bonemorphogenetic protein, and genes coding for the production of bone. 143.The plate of claim 135, in combination with a substance for inhibitingscar formation.
 144. The plate of claim 135, in combination with anantimicrobial material.
 145. The plate of claim 135, wherein saidbioresorbable material is at least in part bone.
 146. A system adaptedto be applied to the anterior human cervical spine for contacting theanterior aspects of at least two adjacent cervical vertebral bodies tobe fused together, said system comprising: a plate comprising: at leasta first plate segment adapted to be attached to one of the adjacentvertebral bodies to be fused and at least a second plate segment adaptedto be attached to another one of the adjacent vertebral bodies to befused, said at least first and second plate segments adapted to beconnected to one another and at least in part overlapped to form saidplate, said at least first and second plate segments being in a moveablerelationship to one another along a longitudinal axis of said plate,each of said at least first and second plate segments including: a lowersurface adapted to contact at least one of the cervical vertebral bodiesand an upper surface opposite said lower surface, said lower surfacebeing concave at least in part along at least a portion of thelongitudinal axis of said plate; at least one bone screw receiving holeextending from said upper surface through said lower surface, each ofsaid bone screw receiving holes adapted to overlie one of the cervicalvertebral bodies and being adapted to receive at least one bone screwfor engaging the cervical vertebral body to attach said plate to thecervical spine; said first and second plate segments being configured tocouple together in cooperative relationship so as to facilitate movementof said first and second plate segments in a direction toward oneanother along the longitudinal axis of said plate and to resist movementof said first and said second plate segments in a direction away fromone another along the longitudinal axis of said plate, said first andsecond plate segments when attached to the adjacent vertebral bodies,respectively, are adapted to move toward one another in response tomovement of the adjacent cervical vertebral bodies toward each other;and at least one spinal fixation implant.
 147. The plate of claim 146,wherein said first and second plate segments are configured to limitmovement of said first and second plate segments relative to one anotheralong the longitudinal axis of said plate.
 148. The plate of claim 146,wherein said first and second plate segments when attached to theadjacent vertebral bodies, respectively, are adapted to maintain acompressive load across a disc space between the adjacent cervicalvertebral bodies.
 149. The plate of claim 146, further comprising atleast one bone screw lock adapted to lock to said plate at least onebone screw inserted in said bone screw receiving holes, respectively.150. The plate of claim 149, wherein said at least one bone screw lockcomprises at least one of a screw, a rivet, a cap, and a cover.
 151. Theplate of claim 146, further comprising at least one fastener adapted tofasten together said first and second plate segments.
 152. The plate ofclaim 146, in combination with a fusion promoting substance.
 153. Theplate of claim 152, wherein said fusion promoting substance includes atleast one of bone, hydroxyapatite, bone morphogenetic protein, and genescoding for the production of bone.
 154. The plate of claim 146, furthercomprising bone screws for engaging said plate to the cervical spine,wherein at least a portion of one of said plate and said bone screws isa bioresorbable material.
 155. The plate of claim 146, in combinationwith a substance for inhibiting scar formation.
 156. The plate of claim146, in combination with an antimicrobial material.
 157. A systemadapted to be applied to the anterior human cervical spine forcontacting the anterior aspects of at least two adjacent cervicalvertebral bodies to be fused together, said system comprising: a platecomprising: at least a first plate segment adapted to be attached to oneof the adjacent vertebral bodies to be fused and at least a second platesegment adapted to be attached to another one of the adjacent vertebralbodies to be fused, said at least first and second plate segmentsadapted to be connected to one another and at least in part overlappedto form said plate, said at least first and second plate segments beingin a moveable relationship to one another along a longitudinal axis ofsaid plate, each of said at least first and second plate segmentsincluding: a lower surface adapted to contact at least one of thecervical vertebral bodies and an upper surface opposite said lowersurface, said lower surface being concave at least in part along atleast a portion of the longitudinal axis of said plate; at least onebone screw receiving hole extending horn said upper surface through saidlower surface, each of said bone screw receiving holes adapted tooverlie one of the cervical vertebral bodies and being adapted toreceive at least one bone screw for engaging the cervical vertebral bodyto attach said plate to the cervical spine; said first and second platesegments being configured to couple together in cooperative relationshipso as to facilitate movement of said first and second plate segments ina direction toward one another along the longitudinal axis of said plateand to resist movement of said first and said second plate segments in adirection away from one another along the longitudinal axis of saidplate; and at least one bone screw lock adapted to lock to said plate atleast one bone screw inserted in said bone screw receiving holes,respectively, at least one of said plate and said bone screw lock beingelectrified for purposes of stimulating bone growth and contributing tobone fusion.
 158. The plate of claim 157, wherein said first and secondplate segments are configured to limit movement of said first and secondplate segments relative to one another along the longitudinal axis ofsaid plate.
 159. The plate of claim 157, wherein said first and secondplate segments when attached to the adjacent vertebral bodies,respectively, are adapted to move toward one another in response tomovement of the adjacent cervical vertebral bodies toward each other.160. The plate of claim 157, wherein said first and second platesegments when attached to the adjacent vertebral bodies, respectively,are adapted to move the adjacent cervical vertebral bodies toward eachother in response to movement of said first and second plate segmentsmoving toward each other.
 161. The plate of claim 157, wherein saidfirst and second plate segments when attached to the adjacent vertebralbodies, respectively, are adapted to maintain a compressive load acrossa disc space between the adjacent cervical vertebral bodies.
 162. Theplate of claim 157, wherein said at least one bone screw lock comprisesat least one of a screw, a rivet, a cap, and a cover.
 163. The plate ofclaim 157, further comprising at least one fastener adapted to fastentogether said first and second plate segments.
 164. The plate of claim157, in combination with a fusion promoting substance.
 165. The plate ofclaim 164, wherein said fusion promoting substance includes at least oneof bone, hydroxyapatite bone morphogenetic protein, and genes coding forthe production of bone.
 166. The plate of claim 157, further comprisingbone screws for engaging said plate to the cervical spine, wherein atleast a portion of one of said plate and said bone screws is abioresorbable material.
 167. The plate of claim 157, in combination witha substance for inhibiting scar formation.
 168. The plate of claim 157,in combination with an antimicrobial material.
 169. A plate adapted tobe applied to the anterior human cervical spine for contacting theanterior aspects of at least two adjacent cervical vertebral bodies tobe fused together, said plate comprising: at least a first plate segmentadapted to be attached to one of the adjacent vertebral bodies to befused and at least a second plate segment adapted to be attached toanother one of the adjacent vertebral bodies to be fused, said at leastfirst and second plate segments adapted to be connected to one anotherand at least in part overlapped to form said plate, said at least firstand second plate segments being in a moveable relationship to oneanother along a longitudinal axis of said plate, each of said at leastfirst and second plate segments including: a lower surface adapted tocontact at least one of the cervical vertebral bodies and an uppersurface opposite said lower surface, said lower surface being concave atleast in part along at least a portion of the longitudinal axis of saidplate; at least one bone screw receiving hole extending from said uppersurface through said lower surface, each of said bone screw receivingholes adapted to overlie one of the cervical vertebral bodies and beingadapted to receive at least one bone screw for engaging the cervicalvertebral body to attach said plate to the cervical spine; said firstand second plate segments being configured to couple together incooperative relationship so as to facilitate movement of said first andsecond plate segments in a direction toward one another along thelongitudinal axis of said plate and to resist movement of said first andsaid second plate segments in a direction away from one another alongthe longitudinal axis of said plate; and at least one bone screw lockadapted to lock to said plate at least one bone screw inserted in saidbone screw receiving holes, respectively.
 170. The plate of claim 169,wherein said first and second plate segments when attached to theadjacent vertebral bodies, respectively, are adapted to maintain acompressive load across a disc space between the adjacent cervicalvertebral bodies.
 171. The plate of claim 169, wherein said at least onebone screw lock is removably coupled to said plate.
 172. The plate ofclaim 169, wherein said at least one bone screw lock is adapted to becoupled to said plate prior to the insertion of at least one bone screwinto at least one of said bone screw receiving holes.
 173. The plate ofclaim 169, wherein said at least one bone screw lock is configured tomove from an initial position that permits the insertion of at least onebone screw into at least one of said bone screw receiving holes to afinal position that is adapted to extend over at least a portion of atleast one of the bone screws to retain the bone screw to said plate.174. The plate of claim 173, wherein said at least one bone screw lockis adapted to be rotated from the initial position to the finalposition.
 175. The plate of claim 174, wherein less than a full rotationof said at least one bone screw lock rotates said bone screw lock fromthe initial position to the final position.
 176. The plate of claim 173,wherein at least a portion of said at least one bone screw lock slidesfrom the initial position to the final position.
 177. The plate of claim169, wherein said at least one bone screw lock comprises at least one ofa screw, a rivet, a cap, and a cover.
 178. The plate of claim 169,further comprising at least one fastener adapted to fasten together saidfirst and second plate segments.
 179. The plate of claim 169, wherein atleast a portion of said lower surface of said first plate segment isconfigured to interdigitate with at least a portion of said uppersurface of said second plate segment.
 180. The plate of claim 179,wherein said at least a portion of said lower surface of said firstplate segment and said at least a portion of said upper surface of saidsecond plate segment include at least one ratchet.
 181. The plate ofclaim 169, wherein at least one of said first and second plate segmentsis configured to receive at least a portion of another one of said firstand second plate segments therein.
 182. The plate of claim 169, furthercomprising at least third plate segment adapted to be connected to atleast one of said first and second plate segments to form said plate.183. The plate of claim 169, in combination with a fusion promotingsubstance.
 184. The plate of claim 183, wherein said fusion promotingsubstance includes at least one of bone, hydroxyapatite, bonemorphogenetic protein, and genes coding for the production of bone. 185.The plate of claim 169, further comprising bone screws for engaging saidplate to the cervical spine, wherein at least a portion of one of saidplate and said bone screws is a bioresorbable material.